It has longer range and it can stun vehicles
Stun is simply OP if it lands and it if it becomes homing it will land. Two infatry section can stun lock a vehicle.
If it is not homing and does not stun vehicles it if fine for Ro.E.
I disagree with the stun.
By all means, the HBG is a normal satchel (just tested it, does the same amount of damage, same fuse, same range). The HGB costs 5 mun more though.
A normal satchel does engine damage if the vehicle does not drive away, the HGB only does a stun. So actually you pay more for the HGB and get less, at least AT wise. Don't know about the exact AoE damage profile, but I assume they're very similar too. And the Penal satchel does NOT cause gameplay/balance issues.
I don't see why this topic should be an issue at all. The only combination might be smoke + HGB, but that is probably a smaller issue that can go live. Balance team has more important things to sort out at the moment than this, so the time can be used elsewhere way better than on this single combination where at least I am not even sure if it will cause problems at all.