Easy to say when your favorite factions
Let try to avoid "favorite factions" comment, they are simply nonconstructive.
have nuke grenades as part of their core army
Its faction has certain things that stock that others factions do not.
Some times and mostly when these things are basic tools they might lead to disadvantage in some area. For instance WFA not having flamers or OKW/USF not snipers is a disadvantage.
HE Grenades don't really create any meaningful disadvantage.
while the Soviets do not even have any grenades available to them in half their doctrines.
Well that is technically incorrect since molotov are grenades and satchel can also work as grenades.
One could even argue that Ostheer/USF/UKF lack stock incendiary grenades.
As for how many doctrines do not have HE grenades that is 8 of 22 which closer to 1/3 than half.