ES 6.3 flush documentation states:

"The flush process of an index basically frees memory from the index by flushing data to the index storage and clearing the internal transaction log"

However in ES 6.0 breaking changes section it's stated that:

"Translog files are now kept for up to 12 hours (by default), with a maximum size of 512mb (default), and are no longer deleted on flush"

Does the transaction log get deleted on flush or not?