Hello.
I use Google Chrome and interested, does for me uploading photos works like for you.
1) create album
2) start to upload photos
3) open new tab in Chrome and do something
4) back to your album
Result: I can see that photos wasn't uploaded while I did something in another tabs. Uploading continues when I back to new album.
Uploading photos pause while I do something in other tab, and release when I comming back.

Is it works as supposed?

Thanks.