Not really trying hard. That is something off the cuff. Exploits are the effort/reward of hacking. If you want to exploit software you HAVE to use 3rd party tools.
Wrong.
Using how code works to get unintended results is exploiting, typically done through the use of bugs known or not, but also done using mechanics in a way not originally intended. What is being done is exactly this, changing mode to bypass the timer mechanism on BB mission replenishment, something that FD is aware of and hasn't stated is something they frown upon to date.
Cheats/hacks are used to BYPASS how the code is supposed to work, such as aimbots, wallhacks, unlimited ammo/health, and so on.
A rather marked difference there, and one that's rather well known, and not just in the video game world I might add.
Now, as I said, and as others have said, this particular exploit is not one that FD has stated is something they care about to date and they are fully aware that people have been using it to get naval rank via charity missions at certain stations. I would guess they didn't care because the manner of the exploit is COSTING the players credits, so the gain in rank is actually costing them what it should in game costs, they are just bypassing the time requirement. Since even FD has noted that naval rank progression is subject to some rather odd bugs, they've decided it's not an issue, after all, credits are being spent, so there IS a drawback for the players, it's not a win/win exploit.
With the way it's being touted NOW, to bypass the BB replenishment and get mission faster to make credits faster, THAT could be something FD has an issue with as this is a pure win/win exploit on the player's part, and those are the types of exploits that devs tend to frown upon and take action on.
Anything that is too good to be true in a video game IS too good to be true and something will be done about it by the devs sooner or later, this is a truism for online gaming and has been for decades now. So, in this case, odds are FD will change how the BB mission refreshing works so that changing modes doesn't work anymore, simple fix really, without messing up how RES's work so that resetting the instance to change spawns will still work. It will mess up people trying to rank up quickly, which isn't something FD has had any issues with publically, what they really think about it behind closed doors, we don't know, but I rather doubt DB was happy about that, he's never been happy with people doing things to bypass his intended mechanics after all.
Or they could just say 'who cares?' and let it go, we don't know, we won't know until they tell us, all we DO know is they are looking into this now.