The point was that no one is complaining about Allied satchels and nuke grenades being very good antigarrison tools doing huge model/hp damage, while for some reason everyone is going apeshit about OKW flame grenades that barely kill one model before exiting the building.
We are talking about garrison denial. Good players dodge high explosives and then jump back in easily unless you do a really nice set up, in which case you deserve that reward of high damage.
Flame grenades keep burning, stopping you from getting back in. I suppose satchels do too but they are also more expensive and on a specialised squad. By destroying the building they also deny its use to the soviet player as well which may not be desirable.