I accept all this but going back to my original post - has anyone ever encountered a WG with an sti at all? It's all speculation.
To answer your actual question, yes, I have encountered a wg who admitted to having an sti.
It was a few years ago, and she posted on auto-censored's board, saying she had caught gonorrhea in her throat (from giving owo), and would therefore no longer be doing owo.
So she was a wg who didn't do bb penetration, but still got an sti. And we know the risk is even greater from bb penetration.
She was brave to admit it on a public forum - I suggest that most people wouldn't admit it, and would prefer to keep it quiet.