Thanks for all the replies.
@Vilas and tubby - I was of similar opinion in that logically LOC and GS should be a selected mode however the FCOM did list LOC, GS, FLARE etc as managed.
The FCTM (SI-030) describes FG strategies in the event NAV ACCUR is LOW (and NAV ACCUR check is negative). In this situation we should display ROSE LS and use selected modes. This was primarily my question. (i.e. use APPR mode or TRK/FPA)
So Lookleft I can assure you i am not worried as to whether LOC and GS is defined as managed or selected while conducting an ILS approach with an FMS operating in HIGH accuracy. Merely a question of "What if" and interested in other opinions.