Hey Maako, sounds like you’ve had a rough time of it… I hope this week is going better for you 
To Simon’s point, and since you’re interested… here’s a book of a post to feed your curiosity
We had a lot of “back and forth” with this feature, so when it finally came down to “let’s get this to customers before Christmas so that offline photos actually work”… this is what we ended up with.
Is it perfect? No. Will we keep iterating on it? Absolutely.
When the first version of photo gallery was released internally, it was “device initiated opt-in”. Meaning that anyone with your device and the 4 digit pin that you totally didn’t set to 0-0-0-0 could download all of your photos.
We were changing the way we treated your data, and I’m strongly against that without an explicit opt-in via a password protected page.
A compromise was proposed… what if we just download new photos since they enabled the feature? No historical images… just this one?
The sync engine was built based on that plan while we discussed this.
Fast forward a few weeks - we’ve decide that the right thing for us to do is to keep that toggle in the rabbithole. But the engine is complete 
So now we are faced with two options:
- Delay the release of local photos
- Only sync photos once’s the device is opted in
As you can see - we decided to ship it. We’ll never be able to make everyone happy with a v1 release - but one of my favorite things about working here is that I know our team wants to create a magical orange box that people love… and we’ll keep iterating to make it better.
Hope that helps, have a good weekend!