This says to me he has very little knowledge of sexual health, or he's potentially going to ask for bareback.
I usually educate on inaccuracy, and invalidity of STI certificates. I've has some very difficult moments with punters who act as if I'm being unreasonable when I won't let them touch my labia or clitoris with their bare penis, won't let them ejaculate over my bare genitals. They offer to show me their test results, stored on their mobile phone. Makes no difference, I will not engage in those activities.