That’s pretty good going for a game that released less than 24 hours ago.
Given the games are so similar, then perhaps CS2 supplanting the Steam page of its predecessor is reasonable.
I’m unconvinced, however.

I think it’s a question of degree.
Valve themselves obviously feel as if the changes between the two games are significant.
They have, after all, called this Counter-Strike 2 and not CS:GO 1.6.
User reviews exist to give players information about a game before they devote time or money to it.
Where that game or its reviews may have changed significantly, Valve normally attempt to make that context clear.
Perhaps all the pre-September 27th reviews could have “CS:GO Review” written at the top.