Lazyeight,
Orbx directions for their libraries being at the top is predicated on the user only having ORBX/OZx scenery on his FSX installation.
IF ORBX is at the top of the FSX Scenery Library and you have 3rd party scenery like RTMM below the ORBX files it can cause RTMM not to display properly or not at all due to the ORBX scenery using excludes etc. in their scenery which could eliminate 3rd party scenery listed below ORBX that is within the ORBX scenery area. As RTMM is scenery within the ORBX PFJ scenery area this is why the files need to be
above ORBX in the Library and that requires an insertion point for the ORBX files because FTX Central will always push ORBX/OZx to the top of the FSX Scenery Library. Contrary to what the instuctions say about these files needing to be at the top the
do not need to be. If you do not make an insertion point as directed then the RTMM sceney will not show up correctly and there is nothing anybody can do about it.
Moral of the story is make an insertion point and enjoy both RTMM and ORBX scenery without any problems or do not make an insertion point and forget 3rd party scenery located within ORBX scenery areas working properly if at all.
To alleviate your concerns nobody has a problem with it set up this way.