It's game vs. realism here. That same grenade that can hurt an unshielded ship might not even one-hit kill a person, certainly not an SRV. Reason ? Balance. Fdev are trying the impossible, creating an environment where everyone can deal significant damage to everyone. Realism would dictate that a person on foot can diddly-squat against ships unless either boarding a ground vehicle or fixed gun emplacement. Realism would also dictate that the person on foot would be instantly incineracted by ship weapons unless protected b a vehicle or fixed gun emplacement.
I don't like what FD are doing here at all.
Like in Real life it Depends on the circumstances, a few Divers could take out a Battleship while is not moving with the right charge.
And a single Soldier can take out a Tank that was made to withstand massive damage, multiple ways.....
So isn't that easy to say it's not realistic.