"Upgrade" an UP fare later?

So I'm seeing some odd things with trying to book a flight... DL website shows the First/Business column with "Business (D) + Other". The "Other" happens to be H in econ. This is coming up on both outgoing and return legs of an itinerary.

I checked the fare basis, and it is the old school (not /wnup) x-up fare HA14UPNQ for all segments. My guess is its going into coach for two of the (short) segments since according to EF, P inventory is not available.
Fare rules are:
INSTANT PURCHASE FIRST TRAVEL
THESE FARES APPLY FOR FIRST/COACH CLASS SERVICE. BOOKING CODES H P D

I seem to remember some people talking about booking these kind of UP fares into coach and then calling later to move into first if the proper bucket is available available. Has anyone tried this recently?

Is this a broken fare? H shouldn't book into D for international BE. OTOH, since it's going into P rather than G or A, I guess this H is considered to be a fairly high fare class. I just would have expected H-UP to book into I and maybe A.

Its 'domestic' BE which could be what is letting it do that. Yeah normally I've seen these HUP fares book into A or I, never D/P... but whats what the fare rules say.

I don't see the fare filed for the individual segments, only on the married round trip, so don't think it can be broken.

I bought one of these where the first hop was a CRJ-200 with a single class. In the 2nd case, It was D+H with the H on a MD-90. Since booking, the price dropped on P fares and I called in and they moved me from H to P without a fee... Not sure if it was because the prices were basically equivalent, or if my fare was supposed to book into P but availability had blocked it at the time.