That makes sense really because when I initially installed Google Photos, it took ages for them all to download, now when I visit, it only requires the latest shots to load. I will have to remember to open it on a regular basis.
I have settings thus:-
google photos >Settings >Back up & Sync >Turn off 'mobile data back up'.
If I don't respond for a few days, it's because I am flying to Cyprus later today, but when established with family, will log into their
home wifi and use my iphone.