I teach my students magenta needle till before the FAF. Then green needles.
How are you teaching?
I don't think the information is conflicting - you still have to monitor the underlying navaid from the FAF onwards. I think the confusing part might be in AIM 1-2-3 c.4 Note 5 "
Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure based on a VOR, TACAN or NDB signal, is allowable."
While Note 5 says it is allowable to use RNAV on the final approach segment, but you still need monitor the VOR as well. The way I have my avionics installed, the HSI
only shows GPS. The VOR/LOC is a separate unit, that only shows that. I like it that way, because there is no possible way you can select the wrong CDI source. So, my G5 is going to show a magenta needle on every approach. Still need to monitor the VOR/LOC on the nav radio's CDI, but the GPS based HSI is much easier to fly, shows wind and ground track, etc. I also like that more, because I'm almost never using VLOC in real life, and its more redundant being having separate avionics if I ever need that.
Garmin avionics will only show one course CDI at one time as best as I can tell, but will let you add bearing pointers. So you could have a GPS CDI source and a bearing pointer showing the VOR radial you are on. I don't really like this, which is why I have a totally separate CDI for the nav radio. But I do understand it to mean that the bearing pointer derived from a nav radio source satisfies "monitoring" the station. In the case of a localizer, you need to see the raw data (per Note 2), so for most Garmin installations, this must be green needle.
I though my VOR was broken for about a week, until I realized that all 4 VORs I had tried were out of service. Which is about how useful relying on VORs has become.
I think the guidance here could be made more clear by just saying "If you have RNAV, you are in nearly every circumstance better off using the RNAV procedure!"