No offence man, but thats just largely bollocks. I see you dont have much experience. Yes, PGrens will usually defeat Guards at medium/short range, but that says exactly fuck all, as Guards are not in the best spot either, and in fact have a bit of a similar problem. Anyways, a well microed Conscript squad can and will actually win engagements against vanilla PGs - although RNG plays a major role here - and Rifles will do so pretty consistently. Allied elite infantry, be it Shocks or Paras, will defeat PGrens effortlessly.
Schrecked up, PGrens represent a major investment, and yet are incredibly fragile. Shermans frequently oneshot them, and every Medium tank can squish/push them and render them all but useless unless thy are supported by a Pak or an additional Gren squad.
What PGrens are good at is keeping Cons or Rifles from aggressively flanking your support weapons on urban maps, but thats pretty much it. I tend to build them for this niche application, but they are just not useful as either mainline infantry or dedicated AT.
Guards with DP-28 aren't that bad at these ranges either... Might have been RNG
Cons are notihing against PGs on close Range when they don't have PPsHs equipped
Rifles are the best mainline inf in the game PGrens suck against them I agree.
In my eyes their main purpose is supporting Tanks with their hand-held AT because they seem to perform best in this role