Typically bosses will "generate" a very small amount of hate on everyone shortly after pull. Since you are "on the list" a self-buff would generate enmity. This isn't altogether unusual.

Aside: This is a pretty major reason tanks should not pull a boss (or anything really, excepting some long range pulls when nobody else does it) with Provoke, as the "small amount" I mentioned earlier is more than Provoke's 1 point of enmity on raw pull.