Do wheelchair bound people identify as "under-represented in technology"? I don't even know. All I know is that some of them may say yes, and some of them may say no. So we don't know who is in the 81%.
Gay - are gay people "under-represented in technology"? Somehow I doubt it. Again same problem. You're gay. You're part of a minority group, definitely. But are you "under-represented in technology"?
Wouldn't it have been better just to spell out the categories and ask people if they are in them? "Are you white", "how old are you?", "black", "gay", "trans", "female", "disabled" etc?