You seem to say that an aircraft flying westbound along the 090 radial is parallel to an aircraft flying on the 270 radial?
Yes, it is. The lines (routes) have no angular difference, and are by definition, parallel.
How can two aircraft which are either head to head or in trail be flying parallel?
This statement demonstrates exactly why you can't/shouldn't be using
lateral separation for either example described. You are admitting the aircraft are longitudinal, and trying to say that is why they aren't parallel!! Then turn around and advocate the use of a lateral standard in a longitudinal situation!!!
That isn't ATC it is simple geometry!
You'd better believe it!!
Perhaps you are mixing this up with the fact that an ATS route may pass over the VOR following the 090 radial inbound and the 270 radial outbound
I'm not mixing it up- it is the example you gave. The wording of Doc 4444 uses "different routes" for a reason- trying to say that two aircraft flying down a single airway which passes over a VOR are "different routes" because they are on different VOR radials (the 090 until over the VOR then on the 270 radial) is really clutching at straws and trying to bend the wording to suit your argument. Once again, the "reasonable man" test would bring you undone, and I can't believe any oversight authority would allow that interpretation. Topdrop further complicated things by adding the arrival/departure element, but I still disagree with his version (for the same reason- misapplication of a lateral standard in a longitudinal situation).
You then go on to say that you believe you can't use the standard for two aircraft pointing at each because they will be too close before lateral sep is lost and the vertical must be in place!!! Either you agree with the standard, or you don't!!!! You want to
infer things (from the "diverge" term), even though you are quite happy to misapply the standard by using loose interpretation of other, clearer, words!!!!
To me, it is absolutely clear what the intention of the wording of the standard is. I just hope Topdrop has misunderstood the derivation of whatever standard he is talking about.