I am able to test my application with 5.0.2 and verify the issue "@MapKeyJoinColumn is creating un-necessary DB update" still exists in 5.0.2.

P.S: I am not able to test with 5.0.8 or 5.1.0. With 5.0.8 and 5.1.0, i am getting "org.hibernate.cache.ehcache.internal.nonstop.NonstopAwareEntityRegionAccessStrategy cannot be cast to org.hibernate.cache.spi.access.CollectionRegionAccessStrategy" exception which is already logged in -
https://hibernate.atlassian.net/browse/HHH-10418.