I think you're moving the goalposts here. He wasn't asking you to share his enthusiasm about her future prospects. He was merely stating that she had an impressive run at this particular tournament (and that's undeniable - damn, you even agreed with that) and your response was to put an asterisk on it. You're being no different from the hordes who dismiss Graf's achievements, because Seles was stabbed, or who lambast Nadal for winning USO without having to play against the top crop (newsflash people - if they weren't good enough to beat lower ranked players, chances are they wouldn't have beaten Nadal too). The principle behind it is just the same. So yeah, you've congratulated her only to diminish her results right after. The way I see it, you either agree it's a good run, with the caveat that you're still not sure about her overall consistency, or you just plainly say that this run isn't as impressive as it is made out to be. That passive-aggressive approach, though, is unbecoming of you.
Not to mention your arguments are as solid as a sand castle. You've injured players all year long (right, this is the tail end of the season and, as such, the probability may be higher, but it isn't a sure thing - besides that, they all more or less went through the same wear and tear) and basically all tournaments taking place right before a big competition may be taken as an example of occasions where most players are afraid to give their all, in order to avoid unwanted injuries.
All in all, stop being a buzzkill, man. I know you like it, but give it a rest.