The sound we use today in "put" isn't [u], it's [ʊ]. Today, it would definitely not be considered an adequate rhyme for [u:]; would you call "look" [lʊk] an inexact rhyme for "Luke" [lu:k]?

On the other hand, I tend to suspect that [u], if it occurred, would be accepted as an exact rhyme for [u:]. Any line-final [u] in a poem would sort of necessarily be promoted to [u:], though.

On an unrelated note, are there areas that use a [lʊv] pronunciation of "love" today? That might explain the to-me odd use of "lurve" in humor.