Possibly big problem with Yoshi's "two sides" mechanic

[curl-6]

Maybe I'm just missing something, but this really bugs me.

Watching the Treehouse stream, it seems that in single player, you can't switch sides at will, and have to replay the whole level to see the other side.

That just seems incredibly tedious and annoying, to have to memorise what was on the other side and play the same stage multiple times instead of just switching back and forth dynamically.

Thoughts?