Oral Sex With Husband Who Does Not Secrete mazi? permissible

assalamulaikum, My husband does not discharge mazi during sexual activity at all, ever. He appears to be one of the rare casses of men who do not ejeculate pres-seminal fluid. With this in mind, would it be permissible, or at least less makruh than if he did secrete mazi, for a wife to kiss and suck the husband's penis, seeing as there is no danger of the najis of mazi entering her mouth? kindly advise. wassalamualaikum.