There are some differences between time attack and regular gameplay for the action stages.
The most obvious one is checkpoints being removed in time attack, but there are a few more. In regular gameplay, there are some 1-up items, but in time attack, they are all replaced by max boost items. Also, for Sonic only, special stage entrances are not present in time attack. Easy mode also affects some action stages, but as far as I know it only removes some enemies.