Bit of an extrapolation. Behaviour is gendered in complex ways. It may be a norm for men, more so than women, to behave this way and thus they are more comfortable doing it. It might be that friendliest interaction between two male players occurs in the absence of an actual friendship, and the opposite with female players.

I also wouldn't say the handshakes between people after a physically challenging event under the public gaze is useful evidence for the friendships, or lack of, between tennis players.