I finally broke down and...

[Prototype_No.98]

I just don't understand...
Why does the T5-U fleet vet ships have 11 console slots. Whilst the T6 versions only have 10 with a T5 ship ability, yet the T6 fleet ships have 11 with no T5 ability, surely for the sake of reason it should have the space trait as well.

[Pip]

I think if you get the regular one and level it up, you get the space trait which you can then use on any ship. I think they're tying ship traits to purchasable ships, much as they used to do with unique consoles.

[Agathon55]

The way I look at it is:

[T5U] 10 console slots, +unique console. ---- [T6] 10 console slots, +1 boff ability, +unique console, +mastery trait
[FT5U] 11 console slots, no console. ---- [FT6] 11 console slots, +1 boff ability, no console, no trait

So T5-U is comparable to T6. While FT5-U is comparable to FT6.

But like Pip said, once you've unlocked the mastery trait, you're free to use it on any ships available to that captain even if the ship is dismissed.