I'm not sure where your getting this from, a phone number is _optional_ for CSGO, adding one is said to improve your "trust factor"[0], theoretically improving your matchmaking experience.
I don't believe TF2 has any sort of phone number system that I'm aware of. If there is one, it doesn't seem to function very well given the bot invasion over the last few years.
I don't believe TF2 has any sort of phone number system that I'm aware of. If there is one, it doesn't seem to function very well given the bot invasion over the last few years.
I can't speak to dota 2 as I've never played it.
[0] https://help.steampowered.com/en/faqs/view/00EF-D679-C76A-C1...