The Welsh player got there first and almost certainly had his hand on the ball at the same time as the ball was touching the ground, but whether the downward motion had turned into his hand slipping off rather than pressing down by the time the ball was touching the ground isn’t clear from still images we’ve seen and is more doubtful than I felt when I was watching it (through red-tinted glasses!) at the time.
I still think it’s likely that more TMOs would have given it than would not have. This seems to be more evidence that we’d probably have decisions which were more understandable to fans if the on-field officials had to make a decision, which they then referred to the TMO. I’d actually ask them to make a decision on any contentious issue they saw, so here Garces would have to decide whether he’d call a knock on if there weren’t a TMO and whether he’d say it was grounded for a try. (He would probably have said no knock on and doubt over grounding, Welsh scrum 5, so the result would have been the same!)
I still think it’s likely that more TMOs would have given it than would not have. This seems to be more evidence that we’d probably have decisions which were more understandable to fans if the on-field officials had to make a decision, which they then referred to the TMO. I’d actually ask them to make a decision on any contentious issue they saw, so here Garces would have to decide whether he’d call a knock on if there weren’t a TMO and whether he’d say it was grounded for a try. (He would probably have said no knock on and doubt over grounding, Welsh scrum 5, so the result would have been the same!)