While it's not unusual for various basses to have a different "feel" with the same string - 2.5mm (>6/64) seems on the high side - especially with your condition you describe.
Is that how your other basses are set?
Let's get back to the luthier;
If he just adjusted the nut, as requested, there are other factors that would prevent lower action; primarily the condition of the frets.
A qualified luthier or tech should be able to provide you with a "summary", especially if you explained your condition and objectives with the bass.
The summary might include before and after measurements of; Relief, string height and measurements relative to the nut (slot depth or string clearance at the nut) but most importantly; any condition that prevented achieving a lower / or the desired action; i.e. uneven frets.
If he just adjusted the nut, as requested,
The nut height was the 1st thing I suspected, and the luthier may have adjusted it - but that's just part of the set-up process.
The condition of the frets will affect the overall setup; if the frets aren't all quite level (and this isn't a-dressed) the setup might result in a slightly higher set up.
That is such a great explanation.
What I have noticed is that Luthiers and techs in the UK do not go to the lengths you describe. They just say, 'here you go, it's ready, play it'. Problem is that I'm not very confrontational and didn't really notice how the stiffness was still bad until I got home.
I agree about the frets as I do think there's something going on with the levelling and he said he would have charged me more to do that, but that it wasn't required unless I want very low action.
The action I have to avoid buzz no matter what I do with the relief is still too high to slap a lot for example and is higher than I prefer for sure.
I'm not actually convinced he did anything to the nut at all. Just because he said he did, he also said it wasn't much that he took off and I am a bit suspicious.
When looking at the intonation at the 1st fret, should it be dead on without any even 1 cent difference?
Anyway, thanks it's food for thought.