If the steering wheel straight ahead is now offset they have probably adjusted the tracking only on one side. This is incorrect and lazy.
Stronger self centring can be a natural result of replacing worn/sloppy joints, (as slack has been taken out of the suspension/steering) or may be a result of having more toe in now.
The self centring on my Leaf was not very good, and tended to wander a bit at motorway speeds, when I checked it a couple of years ago it was parallel rather than toeing in, after adjusting toe in to the middle of the acceptable range the self centring was much stronger and it is more stable on the motorway.
Too much toe in will make the self centring too strong and wear the tyres prematurely.
In a modern car with steering wheel angle sensors you really don't want to be driving with the steering wheel offset - it may cause premature triggering of traction control / ABS.
I would politely point out to them that the steering is offset now and ask them to recheck (check for the first time ?!) the toe in. Toe in/out is one of those things I measure and adjust myself as it's rare that you'll get someone who does a good job of it especially if it was brought in for another purpose rather than specifically to have the wheel alignment checked.
Adjusting the track rod on only one side causing a steering wheel offset is amateur hour.