I'd rather that than him just keeping time to it, seeing as the riff is repeated so many times.. not including the amount of times we've heard it on TGC. It seems the idea is to give it a bit of variance each time around, and IMO his 'drum solo' part works quite well.. I was actually fairly impressed, dug the groove, and upon listening to the drums as a whole dig what Axe brings to the band.
Also, the drum production on this album is the best I've heard on any Opeth album. Said a few words about this on the Sneap forum, but the crux is that Axe really seems to have a more metal approach, which lends itself to punchier drum sounds. Given the relatively thin and dry drum sound on Ghost Reveries, this is a really great change.
EDIT: I don't suppose you have any footage of Axe doing that take around, do you Mike? There's nothing better than seeing drummers pull some magic in the studio... it tends to break up the monotony of recording the other 98% of the drum parts on a CD, hahah.