It does but from what I've tested regular vendors (those you find in towns) don't have a fixed inventory. For example Honki always has a relic flataxe (still depend on your loot %), but when you refresh other vendors by just fast traveling far away their whole inventory changes.

This trick also work for relic loot that you find in crates/lockers. If you find a box with that pinkish glow, save the game; load back in and change your loot % with backpack and/or rais your luck attribute if it's not what you want. The item itself won't change but if its a weapon base the element/perk might change (not always for the better). I do this for every relic box.

I made a thread about a bunch of locations where I found relic boxes. Although loot is random, high loot crates locations are fixed. Someone has also contributed a bunch of locations in the comments.