Does the NEC allow EMT to act as ground?
NEC recognizes steel conduit as ground. One recently active ignorant inspector does not change code, unless you have the same ignorant inspector and opt not to fight them.
You can choose to transition to NM cable in the attic (ground wire connected to the steel box at each end of the cable), though I would not recommend that (I've seen far to many gnawed-bare NM cables to trust them in likely rodent habitat) but you absolutely cannot &quot;staple up THHN wires&quot; without conduit around them. While it may not matter for your application, you are also then limited to the 60C column for wire derate, and if it's a hot attic that might impact you.