A single Astral, with no other source of fighter bays in your fleet does better with 1 broadsword and 5 bombers than just purely 6 bombers. If your only source of fighters is an Astral it is nearly always a mistake to give it 6 bombers instead of adding a fighter, since there is no distraction to prevent the bombers and their missiles being shot down along the approach.
People do have 6 bombers loadouts, because in all examples I have seen, they have filled their fleet with loads of fighters, usually totally more fighters than bombers, such that the entire battle is filled with fighters anyways, thus guaranteeing that whatever the Astral will target will be distracted by fighters and decoy flares anyways. And that is only to be expected since on the way to an Astral, you will likely collected lots of the smaller carriers along the way. When that condition isn't fulfilled, the 6 bomber Astral does poorly. Nobody complains for instance that you can have Herons with 3 bombers, instead of 2 bombers and a fighter, if you have sufficient source of decoy flares. Is it a bad thing that people can use synergistic effects of multiple ship hulls to provide specialist rather than generalist loadouts?
2 or 3 deck with recall device is basically the same "problem". You would be incentivised even more to put purely bombers on it as even a single non-bomber is a significant chunk of firepower removed, half or a third of bomber firepower, whilst for an Astral it is only a sixth of bomber firepower. If all bomber loadouts is to be considered a problem on a ship, then 2 or 3 deck carriers simply encourages more of that "problem".
Btw, I am assuming what you mean by mono-bomber loadouts is 6 bombers which can be different types of bombers, like 4 longbows and 2 Tridents, not literally 6 of only one type of bomber.