I know these privacy things will come up as soon as Google is in a sentence.
The logic is simple, if Google wants to mine my data then they should offer everyone unlimited storage without any string attached. This way they will attract lot more people and mine lot more data.
Secondly, it isn't Apple isn't mining your data, they absolutely are.
Thirdly, Google photo is slightly compressed without loading too much details. As long as it can produce reasonablely print quality if I want print, then it is good enough for me.
Forthly: if I am going to get ads, I will gets ads regardless, I would rather Google mine my data and provide ads that I can benefit from. I don't need ad tells me to buy something I don't need, I need ad tells me something that I will need