It looks like it did - placing the "old" blueprint shows solar panels with old values, but after building it manually the solar panel has the upgraded production. Thanks!
The issue still persists when using Klonan's Kruise Kontrol mod (https://mods.factorio.com/mod/Kruise_Kontrol) to revive ghosts, but since it hasn't been updated in years I don't think that's such a big issue. It's probably that mod's bug with raising events properly or something like that, I'll check it out when I can. For this mod I think the issue is solved, if anyone else is using KK, beware of its possible issues. :)