It does affect the fairplay, but most of the people who do that are higher levels, with whom the 1 given up fight doesn't lower their fairplay value since that's just a droplet in the ocean.
I believe the "Fair Play" percentage is only used to track time outs, and not resignations. Many people (including myself) feel that resigning in ELO once you've definitely lost is good, because it saves both you and your opponent time.
Fair play gets affected by timeouts, not by withdrawal, no matter what room you're in.
I've dropped out of a few and not seen a change in percentage, like above I don't see the point of continuing in ELO when its a guaranteed loss, so resign and get to next battle and opponent gets win he was going to get anyway.
Abandoning a fight does not affect your fair play rateing, only time outs do.
Hope this helps.
"For example, if you time out or abandon a fight and you're on your 100th battle, your fairplay will then have a value of 99%. - - Please note that fairplay increases provided the number of abandoned or timed out fights is lower than the total number of fights played."
If abandoning the fight didn't affect fairplay, why is it mentioned twice in the game rules?
Outdated text; should really be revised. I don't even think it was like that a few years ago, but it could've been like that when that text was first written.
Either ways, it isn't like that anymore.