Does the 256GB version of the M2 MacBook Pro have a slower SSD?

A fuss in Apple country, the 256GB version of the new MacBook Pro with M2 processor and Touch Bar would have a much slower SSD than the more expensive variants with more storage. Is that correct too? Partly yes, but there are nuances to be made in the claims.

Apple had sent reviewers around the world 1TB models of the MacBook Pro with M2 processors, so the reviews published after the embargo expired did not reveal this. Youtubers Max Tech and Created Tech have made videos about it and among others MacRumors and The Verge wrote about it.