Only in cover. And it's still nowhere near the DPS increase that STG 44s/LMG 42/2x BAR/2x Brens give, so the bonus XP gain is still justified. Is the complete package slightly overperforming in terms of efficiency? I'd say over time it has proven so, but the XP gain bonus is not a part of that problem.
Well the complaint by everyone is that the late game soviet mp economy is too efficient. Reducing xp gain on vet and new conscripts, thereby reducing field presence and increasing bleeding, and making reinforce costs 4mp more per model is a direct slight nerf to that overperforming mp economy.