There are a few of the GFE providers I honestly do think are CFS always. Not many and I cannot be 100% sure on that -- some will have a BF on the side and may very well not cover for him.
But the real question I think you're asking in not how much any of us trust the girl is only safe sex but really what are the chances you might get infected with something and take it home. That's a harder question to answer as for some that might be 1% is too much while others might say 10% is fine and yet others might say anything more than 0% is too much. You have to figure out where you stand on that.
Once you do start thinking about the probabilities of some infection if you're covered. For guys the general medical consensus is they are much less likely to get infected by their partner. (I've seen the claims but you should do some searching on the many valid medical sites that are available for search -- or use google scholar to get even better results) It makes a lot of sense. The tissue that covers our dicks is just like that covering our arms and legs and everywhere else on the outside of our body. That tissue has evolved to protect us from such external threats like bacteria. Moreover, the very outside layer is largely made up of dead cells the fall off and are replaced by other dead cells. They generally don't get infected.
Bacteria it self, as it moves from one environment to another, has to acclimate to a new environment. That takes about 4 hours and then the bacteria wills start multiplying -- which is when you're going to be most at risk of actually getting a disease. Just like with everything else (COVID) the simple act of washing well with soap works wonders for killing the infection and preventing disease. So take that post session shower and pay good attention (or tell the girl if she isn't) to junior and the boys. If you're doing sessions longer than 4 hours, just take a quick clean up shower (and I'd say invite the girl to do the same) shortly after you finish having sex.
Also, taking care to be sure you don't have some nick or scrape in your groin area where you could allow the infection under your epidermis where it can find a good growth environment (warm and moist) will help a lot.
Does all that get you to 0% risk. No but I think it gets you well under that 10% level (maybe under the 1%) if you just use some common sense and are spending time with a provider that is likewise practicing good hygiene.