Not a new question. Federer's been doing it that way as long as I can remember.
It's just more noticable now with the asymmetric BLX cosmetics.
If you go back through his pics, 99.99% of the time the "backward, curved side down" Wilson stencil on his strings face-on on the forehand side.
It's industry standard to stencil the frame to match the direction of the logo on the buttcap.
I'd bet he even had P1 install his buttcaps upside down so that his signature was "up" on his k90 frames.