How can you possibly know that? You really think that game developers of those games wouldn't fix these things if they were "bugs"?
I cant know, Im not them, to use farms' example, tell me is it good game design that arrows fired uphill doing less damage should suddenly do more damage if you suicide the unit that fired them before they hit? Sounds more like an unintentional bug. Lets do that in supcom where then you get an artillery that when it fires a shot that shot does more damage if you ctrlk the artillery before the shot landed. Sure it adds "gameplay" (if you can call it that) options, but so does any action a player can take, so to use my previous point, why not allow all the bug exploits that are listed as bannable as well then? Why not terraform when it can be done? Just because it can be done doesnt mean it should have ever been an option at all.
You can just take any game filled with bugs and say that they arent bugs because if they were then developers would have fixed them. How many bugs did faf fix that steam fa still has? Were those bugs at all since gpg didnt fix them? No, it is up to us to decide what game mechanics should and shouldnt exist at this time (because gpg doesnt exist to do that instead), instead of doing nothing about those bugs because we wrongly consider them valid gameplay mechanics.
We should first fix the bug, then balance underwater units once the bug is gone. 2 negatives dont give a positive in game design and 2 bugs dont cancel each other out.