ReeroNot saying the trend doesn't exist, just that bad social treatment of a minority doesn't make them worse at something.
the paper actually agrees with that statement
As explored in Study 1 and supported by Study 2, many female players may be compelled, pressured, or otherwise directed toward playing the Support role that, though requiring no less competence than other in in-game roles (and arguably more), is nonetheless seen by many players as subordinate to, and less desirable than, the role of ADC.
the paper mostly points out that the lack of females in (competitive) video games at any skill level (this is almost assuredly different at top level, just as it is for every sport) has nothing to do with actual skill levels and instead is caused by some other factors and in the conclusion conjectures that it's possibly due to the negative atmosphere in video games towards women.