I could be wrong but this is what i am feeling.
I also use both. Quickpic is also my primary gallery app and i also use Google photos to save my photos as backup.
Before, and till now, quickpic had added the picasa and we could upload only to picasa but as picasa is shutting down and google is shifting to google photos AND quickpic has not yet released an update in their app adding google photos. This might be the problem.
Though i don't use quickpic to upload pix to photos, rather i use google photos app for this purpose.