My understanding of the intuition for why they would be different is that a long read lock hold is less serious than a long write lock hold, since other reads can still proceed. Also long reads may be more expected given listStatus and contentSummary type commands. It is also typical to have a higher percentage of operations be read, so potential spam volume may be heavier for read locks rather than write locks.
That being said, 5000ms may still be a more sensible default, erring on the side of lower overhead unless an operator actually uses these log statements in which case they can tune the threshold themselves. Zhe Zhang, do you have any opinion?