The comment was originally added in 4b831a5d.
At that point, it referred only to non-FFP shader constants. Subsequently
38934fe7 moved bumpenv constant loading to the
misc pipeline, apparently out of concerns that bumpenv constants might interact
badly with shader constants.

It's not clear whether those concerns were ever justified, and normal shader
constants are now sufficiently untangled from each other anyway. However,
bumpenv constants, like e.g. color keys, affect both FFP and non-FFP pipelines,
so it makes the most sense for them to remain in the misc state table anyway.