It's fine to disagree – no reason to get personal.
I think I've had this argument with Europeans a million times on here already, so I usually just agree to disagree, but I'll make my point again here. There are tons of reasons to go pro as early as you can – like you said, players get a salary with basically no living expenses. With a very limited timeframe to earn money, this all makes sense. But from a purely developmental standpoint, I don't think it does.
For starters, staying in (North American major) junior has never hurt a player's development. Even Leon Draisaitl went back to the WHL after half a season with the Oilers. And Draisaitl was in the "way too good for junior" category at the time. De Luca is far from that. He had a decent-not-great year in Spokane. At the same time, there are endless examples of Swiss and German (mentioning them together because they're quite similar in terms of prospect talent level and CHL vs. pro success) prospects who turned pro as soon as they could and never quite panned out. More often than not, playing a top-of-the-lineup role in the CHL with 60+ games with 25 minutes of ice time is preferable to playing 0-10 minutes per game in a bottom-six role in a European pro league, whether it's the NL/DEL or SL/DEL2.
De Luca is one of the best prospects Switzerland has had in recent years. If he played another season in Spokane and returned afterwards, he'd easily step into an even bigger role with Ambrì than he will this year. He might miss out on what, CHF 50,000? But he might get more money more quickly after that, as he comes in with a bigger role as a better player.
I fully understand why many European players turn pro as soon as they can. But I strongly disagree with the notion that there are no downsides to signing with an NL club at 18 when you could play with Berkly Catton in Spokane.
Again, he could get that in Ambrì in a year. There is literally not a single reason to believe Ambrì would only take him now and if he stayed in Spokane he'd have to go somewhere else.
That said, Spokane has some of the most passionate fans in major junior and they frequently fill up their 11,000-seat arena – which is more than Ambrì's arena can fit, if I'm not mistaken. I know the fans don't compare to Europeans and I can only imagine how cool it must be to play in front of the fans in Ambrì. But attendance-wise, playing in Spokane is not the same as playing in Swiss junior. It's a pretty cool experience too.
I don't think so.