i have a tiny hunch that the triss outfit was originally for francesca findabair who i suspect was cut from the game ;~; hence it not *quite* making sense
Francesca might still be in one of the expansions. They could slightly alter Triss outfit for her, no shame in reusing art assets on a secondary character.
I could imagine a Scoiatael / Iorveth / Saskia /Francesca questline. It's clearly something that's missing and would be VERY popular I guess.
No. This outfit is totally out of character for Triss. She would never wear it in the books or in the game. I think that CDPR thought it looked cool and that is about it.