My only issue with this is that, unless you have a personal or professional (in matters of health) relationship with someone, what someone chooses to share with you about their sex life does not entitle you to further information they have not shared. Because it still comes down to a base assumption: "You're having what I deem to be a lot or too much sex, so I'm going to assume you are unconcerned with your sexual health and inquire accordingly." But hey, a question is a question, so go ahead and ask. But some questions are rude.
If I'm having sex with you, or if it's even a possibility, oh I definitely am going to ask about your sexual history. If we're having a general conversation about sexual health and all that entails, then yeah absolutely an environment should be fostered where people feel encouraged to share without judgment. But in this context, when what's stirred the discussion is the call being made that someone's having a lot of sex, then it's iffy for me. Because the judgement is being implied. Because, frankly, most people who are sexually active should be getting this question then. But pay attention to who tends to get asked "...do you get tested?"