Which is relevant how? Not having the suppression to stop them from frontally nading it is absolutely a problem for an Mg regardless of the incoming damage.
It is at least a detail to consider, a well placed HMG can stand better against the marginal example of a riflenade. Trading a single model (30MP) and a skillshot that costs 30Mu for only a slight amount of damage is a bad trade. I think that its possible to kill the gunner if it hits just right, but im not sure about it.
It is relevant since this feature punishes badly placed hmgs compared to well defended positions. Trences and buildings are even better. This simple mechanic teaches and rewards players to use the hmg in a specific way. If you really want to stop grens from using riflenade, you should nerf their fire animation, nerfing overall the gren squad.
I do think that volks lavanade is BS when they can throw it under vickers fire, since it will force the vickers to move and damage the crew a lot more. The volks suppression bulletin is a big issue aswell.
It's impossible for a rifle nade hit to do 10% damage on a direct hit.
I said it does not deal 10%, pls read again. Heavy cover mitigates half the incoming damage. The squad might get hurt by the far AoE, only 1-2 models will receive near AoE dmg. Overall it hurts the creo by 10-20% of the squad health