Whether Crosby is a "clutch SCF performer" has nothing to do with whether he's a top-5 player. It has to do with how well he performs in the cup finals relative to other players.
You're only bringing up the top-5 argument because it's easier to argue "Crosby isn't Gretzky" than actually make a legitimate argument against Crosby being a clutch SCF player.
But if you're going to say that, you need to bring proof that Crosby isn't putting up "momentum influencing points" while Kane is.
Look, I'm not gonna sit at a desk with spreadsheets open digging for excerpts from all his games; you're more than welcome to share any moments/memories you have of Sid coming in the clutch. All I can say is that I recall a fair amount of key/clutch goals/plays Kane has made in the playoffs to earn his reputation, I don't have anywhere near as many memories of Sid doing the same.
Just by searching "Kane clutch" in Youtube, I found this. Obviously this isn't just in the SCF but my OP was about the playoffs in general, which may even strengthen Crosby's argument as clutch applying the same logic:
Here's what I could find for Sid (feel free to share any others this may miss):
Kane is clutch in the playoffs because he scores game tying/winning/shifting goals and gives his team life when a series is in the balance or on the line; he's done it repeatedly to earn that reputation. Crosby has a few of those moments here and there, but his production is more evenly spread.