Many gum clinics dont offer oral swabs ny default, so girls think they are all clear due to ignorance.
They'll offer what people state their at risk for. I go to a specific sex workers clinic, and they swab all, one for the mouth, one for the pussy, one for the arse. Plus the blood vials.
I've even had my eyes swabbed, which is one of the most unpleasant things I've experienced. But important to do occasionally if you allow facials, not for risk to others, but to ensure I don't have anything and go blind.
If you're going to a normal clinic and not disclosing that you're an escort/see escorts, you'll often get a shorter list of tests done. Which is silly as doctors/nurses have legal obligations not to disclose patient's private information. You can also give fake names, not provide your GP information, everything really. Some clinics are even setting up services so you can check your results online without having to worry about calling up/getting a text/email that then has to be explained away.
I will also say this, condoms are not 100% effective at preventing chlamydia and gonnorhea, or a variety of others, which is why it's vitally important to get tested regularly on both sides. They just massively cut the chance of passing an STD, but there is still a small risk.
Hence guys don't leave your tests to just once every 6 months/a year, even if 70% of the time you will show symptoms of infection, the onset of symptoms does vary, and 30% of the time you will be asymptomatic.