What exactly is a glazed trapway?

The ads I've seen for the Toto Drake I just got said that it has a fully-glazed trapway. I thought this meant that the glazed finish of the bowl was continuous all the way through the channel that the waste will go down. But when I put my fingers in there, the surface seems considerably rougher -- not as rough perhaps as the unglazed stuff, but nothing like the smoothness of a toilet bowl. Is this normal? Does it matter?

Most toilets have glazed trapways now.

It's done by pulling a sponge soaked in glaze through it.
It's more to seal the porcelain than anything else.

It's normal.