Let's be pretty damn honest here:
Most guys only go down on a woman during the hot red rainy period, when the (w)hole lust thing is still pretty fresh (lol) & new! In those heady days, the type of underwear isn't likely to make a difference either - but it lays all guys open to the future _ "you never used to mind when..."
As for wallowing in a shower of crimson tears, that's just not on for most, except for vampires, or if you've got carried away & are helping to extricate a tampon!
Frankly, everytime I've had a year's worth of iron in my mouth, I've always insisted on sharing the mineral love!