The reason for this is that Delphi subsector P has non-Imperial allegiances in the classic Atlas. So whoever designed the routes for Delphi (JTAS Online, I think?) skipped that subsector.
For T5SS we corrected the allegiances.
The "metadata" (borders, routes, etc) isn't considered part of the official T5SS data. Suggested route fixes for Delphi etc are welcome (ideally as pull requests)
Interestingly, you don't seem to have corrected the allegiances of three Non-Aligned (Eisner, Corineus, Elke) and two Client States (Iini, Fortescue) in subsector O (Zuma). Was there a reason for not doing so?
I'd be happy to suggest some route fixes, but I'm not sure what you mean by a "pull request". My suggested route amendments would depend on whether those five worlds are corrected (actually, only Eisner would affect my suggestions).
If Eisner is changed to Imperial, my suggestion would be:
Lastir/Zuma (Delphi 2139); Eisner/Zuma (Delphi 2336); Coning/Breda (Delphi 2336); Breda/Breda (Delphi 3035); Mesinam/Verge (Glimmerdrift Reaches 0133); Paradise/Verge (Glimmerdrift Reaches 0131) and/or Sha/Verge (Glimmerdrift Reaches 0432). I'd add a spur from Coning to Frigidair/Breda (Delphi 2833).
If Eisner remains NaHu, my suggested route would be:
Lastir/Zuma (Delphi 2139); Cabra/Zuma (Delphi 2438); Rogis/Breda (Delphi 2839); Dami/Breda (Delphi 3138); Breda/Breda (Delphi 3035); Mesinam/Verge (Gimmerdrift Reaches 0133); Paradise/Verge (Glimmerdrift Reaches 0131) and/or Sha/Verge (Glimmerdrift Reaches 0432). Add a spur from Breda to Frigidair/Breda (Delphi 2833).
Second route to add:
Lastir/Zuma (Delphi 2139); Cabra/Zuma (Delphi 2438); Rogis/Breda (Delphi 2839); Siaj/Rusco (Old Expanses 3102)
I'd also be interested in the background to the two-leg X-boat route [Adar/Adar (Hinterworlds 0401; Imperial); Kaggits/Adar (Hinterworlds 0201; Ral Ranta); Venad/Adar (Hinterworlds 0404; Imperial)]. It would make more sense to delete that and replace it with the following route:
Engle/Rusco (Old Expanses 3204); Venad/Adar (Hinterworlds 0404); Shanka/Vege (Glimmerdift Reaches 0840); Ilaria/Verge (Glimmerdrift Reaches 0837).