It's only an 'exploit' if FDev say it is. If FDev had come out and said it was expoitative useage then I would agree, however although I can't find a reference to the actual statement they made, they did make a statement to the effect it was OK to be used in this manner / not breaking the ToS.
Frontier has made some ambiguous statements about multi-crew and have conveyed their intention to not prohibit the use of additional accounts for extra pips, but they have also explicitly stated that the game was not to be pay-to-win and nothing they'd sell (presumably accepting backer rewards and expansion content) would allow for an in-game advantage over others.
There are quite a few exploits that Frontier tacitly accepts because they cannot do anything about them, or cannot decide what to do about them. This doesn't change what they are. Frontier doesn't even need to be aware of an exploit for it to be an exploit.
Cheats aren't defined by whether one is punished for getting caught, but by whether they provide an unfair and unintended advantage. If you think the intent of multi-crew was for players to buy second accounts so they could play with themselves and get extra distributor pip, I'd argue you have an inferior understanding of what this game has been presented as, assuming you aren't just being disingenuous. Quickly skimming the 2.3 beta threads regarding multi-crew would reveal what the intent of multi-crew was and free pips was not it.
An argument that cheating is ok because they won't stop you would be far more defensible.
The fact that the extra pip for doing nothing is a thing is the biggest joke of MC imo . Where does this extra power in the distributor come from?. Sure I get that if the player in MC was doing something skilled it could perhaps increase performance but "free power" for just buying another account and letting it idle screams "lame mechanic" to me.
It's an abstraction and a placeholder. They never fleshed out the mechanism and wanted to incentivise people to use multicrew, so this is what they came up with. Of course, people abused it.