Takeoff: LNAV is available and commonly selected above 400'RA. Ist clue.
In descent "2500" EGPWS call from RA. 2nd clue.
On finals "1000" call from RA.
I think all these come from LHS RA. There may be different customer options for call outs, but the RA can be seen to be in use before the final approach. There might not be a u/s flag, but there are various scenarios where it can be seen to be correct yes/no. If so, is the concentrating on lack of tech log entry being so significant not a slightly smelly fish.