Well, there was also mention of the Corsair, who did both male and female regerations. Idk, to me, the Time Lords can be genderfluid and it's hard to know if the fact that we see them regenerate into one gender is really true to the characters or just the writers doing the same old stuff over and over again. Just like people who complain about Steve Rogers's bisexuality because he wasn't canonically bisexual 50 years ago. Yeah, of course, nobody was going to say it way back, it doesn't mean it can't be said explicitly nowadays.