pg_last_xact_replay_timestamp meaning

I just applied a doc patch for pg_last_xact_replay_timestamp, and the
text now says:
      <entry>Get timestamp of last transaction replayed during recovery.       This is the time at which the commit or
abortWAL record for that       transaction was generated on the primary.       If no transactions have been replayed
duringrecovery, this function       returns NULL.  Otherwise, if recovery is still in progress this will       increase
monotonically. If recovery has completed then this value will       remain static at the value of the last transaction
appliedduring that       recovery.  When the server has been started normally without recovery       the function
returnsNULL.
 

Is this really the last commit/abort record or the last WAL record? 
What should it be?  Is the name of this function correct?  Do we care
only about commit/abort records? Why?

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + It's impossible for everything to be true. +