The Recaros also fold flat.
The full size spare in the ST means that the rear deck is a inch or two higher than with the mini, which also puts it an inch or two higher than the folded-down rear seats. Both are level, but there's a difference in height between the two flat spots. So, depends on what you mean by "flat". Same with the ST1 seats, as it's the spare that makes the difference, not the seats.