Unless the glass hasn't been fitted into the regulator properly and the water is leaking from a badly sealed window...although having replaced 2 of mine myself I struggle to see how it could be the case...I think you can rule out the window regulator work as a source.
My guess would still be the panoramic roof/sunroof for anywhere around the 2nd row seats with the water seeping down behind the lining/pillar trim and down the B pillar. There's nothing else near there that could be the source of a leak... barring a failure of the front or rear door top seals or lower window seals on that side.
...or a hole in the floor
I know I tend to make fun of dealership
fitters...sorry... vehicle technicians... with their clean, ironed overalls and strange work practises...but it would require some seriously challenged technical muppetery to remove the window glass (or door) to replace a window regulator or muck the job up so badly that the window or door seals leak...
Replacing a regulator is a 20 minute job that only requires 2 torx screwdrivers (T20/T30) and a bit of gaffer tape (or special window locking pins) to hold the window glass up as you're removing/fitting the regulator...there's absolutely no need to be touching the window seals, far less removing them...unless you're replacing the window glass itself.
...but check for your own peace of mind that the outer rubber window seal on the door they worked on is actually there and is touching the window glass, not folded over or anything...and see if there's any sloshing sound if you wiggle the door about
Something sticks in my mind from the old Disco 3-4 perennial issue of blocked sunroof drain channels that the water ran down the inside of the A pillar and fed along the wiring channel under the door kick plates to wet the rear carpets...but that surely can't be the case here... your door sills would have to be full of water leaking down from the windscreen and the front carpets would be wet too in that case
Apart from all that. I'm clutching at straws here...
.