I can tell you that one of the most common benefits to oil pulling (that many including myself report) is that your gums STOP bleeding not long after you start. Two things -
1) I don't think you should regularly exceed 20 minutes.. I do myself sometimes and notice that my teeth and gums can feel sensitive afterwards; and
2) You could be right that it's part of a healing reaction if you have some kind of infection or gum disease.
But overall OP does nothing but make your gums healthier (and amazingly so) if you follow the protocol.