This is true, however when it comes to the girl in question I have a feeling it was due to poor hygiene/wet wiping between clients.
He posted in another thread replying to another punter's review and mentioning he was sensitive to smells, I don't think in this thread he was referring to anyone specifically and it was a general question?
Sex is a messy business involving bodily fluids and for me personally not being totally 'fresh' has never put me off giving oral (other factors have much more relevance). See edit below
The exception is Bacterial Vaginosis (BV) which Davie hinted at and which is can be related to 'over cleaning' or poor choice of soaps/technique. Sexual activity generally is also a trigger so sex work is not really ideal. Some women are considerably more prone to BV than others and it tends to be recurring.
Vaginal floral balance is a complex subject and some women can be a martyr to their love tunnels!! BV is fairly common.
It has a very distinctive and pungent 'fishy' smell which once encountered you will remember.
I personally think you should inform the person that you suspect it, as it requires treatment, though is not really a risk to the punter other than the smell.
I have never told an SP they are not entirely fresh as it is unlikely to change anything, but have told a number where I suspected BV. I did this in a 'delicate manner' and always at the end

This had varying outcomes from 'thank you' to 'fuck off'
External Link/Members OnlyEDIT I should add that a normal healthy vagina is not odourless. It is also to a degree individually variable. I prefer that 'natural' smell to the overpowering smell of cleaning products/ perfumes