That’s just it Tom, it’s certainly “possible”, it’s just unbelievably low to the extent you have to be very very unlucky is what I’m told.
There’s a lot of urban myths around medical stuff, from the old “wrap up or you’ll catch a cold” (impossible) to “urine is sterile” (well if it’s always sterile then why do doctors take samples to test for infections).
He’s your mate, I don’t know him but are you sure he definitely got it from oral and it wasn’t really that he didn’t bag up and didn’t want to admit to barebacking
Half joking there but tell you something, that same nurse friend of mine said he got many people coming for testing because the condom split.... he reckons most were just shy for some bizarre reason to admit to gum nurses that they actually didn’t use a condom. Scared they may be judged maybe