Maybe it's also that the definition of unmarried would include people who have concubines but no main wife?
Because imagining someone with a wife proposing to Lord Nihuang sounds like it could get only messy, as you said. Bad times for everyone involved.
(Imagining Wei Zheng, Just Married entering the tournament and then stage whispering to Nihuang: don't worry, we won't let the young general's family get married to these morons, as a differently amusing thought.)