I have a 2017 Golf Alltrack. The other day I found substantial pools of water on both sides of the rear floor. No water anywhere else. Not rear cargo, not in front floor and no signs of wet or water staining on side pillars or anywhere around interior roof. It is as if someone poured a pint or two of water directly on the rear floor, both passenger and drivers side. Also, no sign of dampness around bottom of doors or seat... only water was directly in the floor where mats sit. I did have an issue back in 2017 with leaking water into drivers foot area but that was fixed by VW and no issue since. That was obvious because there was water staining on roof and front pillar. I was out of country for 2 weeks and we did have a few good rains but I've never had this before. Only other thing is I went to a car wash before I left and had an undercarriage wash. But I have done this many times as well. Very curious as to where it came from.
There are other places that leak besides sunroof, you'll have to research I have and there's about 5 areas where water leaks in other than sunroof.
One area is the door drains which sounds like your issue. As I said you'll have to research on YouTube I know I saw a fix for it. But IIRC it's one of the more involved fixes requiring removal of door panels.
Other areas (not for your issue) back-up camera drain grommet breaks off allowing water to enter cargo area check if grommet is still intact if it's missing and just a hole then you'll have to replace entire hose (there's a video on YouTube showing how) requiring removal of interior plastic panels on hatch to get to drain hose (entire hose has to be replaced grommet is bonded to hose)
Another common area...The rear quarter panel vents a large louvered flap system, the frame is the culprit it allows water to leak into cubby hole storage area on either side of hatch. Removal of rear bumper cover to gain access, fix is remove entire frame clean and reinstall using sealant around loose fitting frame. Be sure to remove rubber plug to drain standing water then re-install plug.
Another area at top of rear hatch rubber grommet for electrics inside hatch leaking water inside hatch...seal grommet
Another area tail light seals can leak, over time these seals can leak remove tail lights thoroughly clean all mating surfaces re-install if leaking persists I won't recommend anything here as I don't want to give bad advise...but I have seen people use sealant which I wouldn't recommend because it will make future removal very difficult.
I think that about covers it at least that's what I recall...everyone that's concerned about leaks should check these known areas.