No I wasn't saying that. What I mean is that all axis support weapon teams, Sturmpioneers, Obersoldaten, Fallschirmjaeger, Jaeger Light Infantry also suffer from the same problem of getting wiped too easily by mortars, light vehicles. So changing the grenadier squad size will not have the same effect.
Grenadiers are mainline infantry and the weakest such right now, with low survivability compared to all other mainline infantry units, well, next to IS but they can get an upgrade to 5 man squads so they don't really count after the upgrade, which any sensible British player would get ASAP.
Sturmpioneers have the same exact problem as any other engineer/builder unit, so they're not a special snowflake here, the difference is here that they're the only ones with hand held weapons now, which makes them, apart from infantry combat duty, repairing and building, an anti-tank role which means they'll be playing with fire and that's why they mostly get wiped, I also think Panzergrenadiers suffer from this as well, but that's another question.
Obers, Falls and Jaegers are all specialized infantry units, 2 of which are call ins even. At most I'd give obers a Faust ability but that's it for them, they're meant to be Anti-Infantry specifically.
Again, Grenadiers are mainline infantry, they're supposed to be dependable, but due to their low survivability they're not like the volks for example. But yeah, making them a 5 man squad right from the get go is one way of doing it, having a universal upgrade like the British one giving them, the Panzergrenadiers and maybe even the Pioneers a 5th man to their squad is another way of doing it, giving them a 5th man along with their weapon upgrades (MG42 and Panzerschreck for the PGs respectively) is a third way.