Since junction point is not defined in article 100, I think we need to look at the common meaning of those words. I looked in two dictionaries in the office and came up with:
1. a joining or being joined
2. place where things join
It sounds like the coupling we're talking about meets this difinition of a "junction point". But (and this is where it gets interesting) so do all of the couplings in a run of EMT for example!
I guess I can't really see any reason to treat a straight through coupling between EMT and some other raceway differently than the couplings in a run of EMT and I'm not ready to start requiring those to remain accessible
I'll have to agree that the only time it makes sense to apply 300.15(F) would be at a cable/raceway transition. Looks like maybe a code change proposal is in order.