Curious why you say that? As you stated, the consensus on him is quite the opposite.
I'm no scout, but I have to imagine that if you're picking a player top-10, you'd like them to have at least one athletic feature that stands out at the NHL level, that you can easily build around; something like Misa's speed, Frondell's shot, Hagens's hands, McQueen's size. Something tangible you know will translate well because you can see it. Right now, Desnoyers doesn't have one of those. He does have a very nice, well-rounded toolkit, but if you were to rank all 2025 draft-eligibles purely on their athleticism, Desnoyers wouldn't be top-10, or even top-15. And those jack-of-all-trades, good-at-everything prospects are not as safe as a lot of people tend to think. He will need to go through a ton of physical development to be a good NHLer, let alone a great one (especially since I think physicality will be an integral part of his game at the next level). Which isn't unusual for a prospect, but as much as fans tend to assume all young guys will automatically get faster, stronger, better, that doesn't always happen.
Now by all accounts, he's a great kid with a great mindset who's always seeking to improve, so I'm sure he'll be an easy guy to bet on. But you can't take all that development for granted. I think that of all the forwards talked about as likely top-10 picks, aside from O'Brien and maybe McQueen, he's the one that's furthest from being NHL-ready right now. And there's inherent risk in that. Yes he plays a "pro game", but a pro game is useless if you don't have a pro body. I've seen people say they think Desnoyers could play in the NHL next year, and I think that's crazy. Unless that kid literally lives in a gym this summer, and even then I'd be wary of keeping him up.
I also think his shot will likely limit his offensive game at the pro level. He has an NHL-level shot, but he struggles to get it off quickly, and he doesn't seem to have that ability great scorers have to be able to get it off even when off-balance and under pressure. I'm sure that's something he can improve, but I don't think he has high goal-scoring potential at the NHL level.
On the flipside, when you have a prospect who's as effective as Desnoyers while having so much runway left in terms of physical development, it's easy to be optimistic about his future. I don't want to undersell his offensive tools: he has nice hands (though he uses them sparingly), hes an excellent passer, he sees the ice well, and he's surprisingly effective on the physical side despite being listed as a skinny 6'2 172 lbs player. And he does so much damage simply through consistently great decision-making, positioning and timing. Great off-puck game. Great at turning defence into offence. Competitive, with an edge to his game (though like most of his tools, it's something he keeps in reserve for when it's needed). There's so much there that should translate well to the NHL.
But not if he doesn't add a good 25-30 lbs of muscle to his frame, ups his pace, and maybe adds a bit of explosiveness and agility to his skating. All things that are well within reach for a driven young highly-touted prospect, but he still has to do the work. And I hope whoever picks him develops him patiently. without rushing him. I've seen someone (at EP maybe?) compare him to Shane Wright as a similarly high-IQ, low-pace center in juniors, and I think the way the Kraken brought him along progressively, without rushing him despite all the hype, is a good blueprint for how Desnoyers should be handled.
I should note, when I say higher-upside, I don't necessarily mean in terms of points. Mostly because I don't think Desnoyers has the raw talent and creativity to be a PP1 guy at the NHL level (unless he develops a specialist skillset, like a faceoffs/net-front guy). NHL teams will always have a couple of guys that are more gifted when given time and space. And that will ultimately limit his production. At the same time, I could see Desnoyers's upside as being a strong, versatile, intelligent center who can enable skilled wingers by driving possession, or run a heavy line that forechecks and cycles opponents to death, or anchor a defensive shutdown line that matchs up with top lines. I don't want to bring up the Bergeron comparison, because it always winds up being off-base, but maybe a player like Eriksson Ek would be a realistic comparable. And that's a hugely valuable player that every team wants, even if it's not the kind of offensive dynamo that fans want to see their team draft in the top-10 (not that you're guaranteed to get that kind of player in the top-10, far from it). People will talk about him being a 1C or 2C or 3C, but I think that can be reductive: some players are a 2C as in "offensive center who's not productive enough to be 1C", some are a 2C as in "center who can be highly effective without getting fed tons of offensive opportunities or top linemates". I think one of those is a lot more valuable than the other.
TLDR: kid needs to hit the gym