I don't see the confusion here. If you have it in your data base, that particular a/c is probably able to fly RTF, which for all intents and purpose makes f'all difference to the tracking, except that it has a high degree of accuracy to be able to navigate precisely from a radial to a fix.
To request it in Hong Kong ( midnight onwards) you simply make the request on the the electronic PDC request in the remarks column.
It is such a strange statement to get others confused, including Atc, when actually verbalised. The reaction from others is likely to be "what was that?"
I have always used the remarks column in the ACARS PDC and it works all the time .