Here is an interesting Rabbit Hole to go down.
We all fly Vor Radials, we all sometime fly Direct-To, and some even fly an GPS OBS radial.
Mostly, these are over relatively short distances ( less than 200 miles), so we do not notice what is really doing on, and how local & destination magvars play into this.
Most also, do not have a detailed understanding of Projection types, and use in MSFS, or as used in real world Aviation.
Over longer distance, Direct-to is NOT the same as flying a magnetic radial to a VOR, that is far away with a different magvar to that where the aircraft is.
In MSFS, due to the Projection it uses, Direct-To over great circle routes is very different to flying an OBS heading to the same distant destination.
Try sitting at NY (KJFK) setting up to fly DIRECT-TO the UK.
Then try setting up to fly GPS OBS to that same point,
Look at the Magenta line on the GPS in both case.
Remember, that you, in the plane are using your local Magvar, while the VOR or GPS OBS, has a magnetic bearing using its local magvar !@!
Things get even more messed up / confusing, if you so this using the MSFS GPS systems, and say the Garmin Trainer (Rea world), each of which use a different projection system …
I never got this deep into these details , before MSFS – have to do something when MSFS starts CTD’ing all the time when I actually want to fly with it !!
Anyone interested in this stuff ?? Any “Positive” thoughts (apart from what does it matter in a sim !! )