Where of course "Asian theatre" is entirely unambiguous ;)

Why - I'm pretty sure the Eastern Front was entirely in Europe?

No, that is the Pacific Theatre. Eastern Front in WWII unambiguously refers to the European theatre of the Axis-Soviet conflict in Western post-war study. The problem with that term is of course that from the Soviet/Russian perspective, the enemy was coming from the West, so they refer to the European theatre as the Great Patriotic War - a rather loaded and mostly unheard of term in the West.

So academia has had to come up with new rather obscure neutral terminology like the German-Soviet Conflict or Russo-German War.

"Eastern Front" is pretty widely understood I would think, perhaps because there wasn't so much of a single "front" in the pacific theatre? (except for the second Sino-Japanese war)

WWI also had fighting in East Asia, e.g. Japan taking Qingdao and various Pacific islands from Germany.