I've seen this on a few Supras now. I have it to a lesser extent on mine. I think its down to having the windscreen replaced at one time or another...a breakage or re-spray perhaps.
On mine, the windscreen got cracked and replaced. The first time the job was done the finishing strip came loose after a few days. I took it back and they did the whole job again...this time the finishing strip stayed in place but is not as good a fit as original....theres a few lumps and bumps along its top edge.
If it helps, the water tightness of the screen does not rely on the finishing strip, as long as the glass has been installed correctly.
IMO, If the glass is installed too high, or too low, or too much sealant is used, the finishing strip cant seat itself and clip in to the rebate as its designed to do.
Hopefully someone else on here who has done this job before can add to this ?