Lollipop Restore Only Wants to Clone Old Phones I no Longer Use..

I've been doing a bunch of installation of new ROMs in different phones.

Generally, the Lollipop restore function works great - when setting up a new phone or an old phone after a factory reset it offers me a list of phones, I choose the one I want, and it installs all of the same apps as on the phone I select from the list.

For some reason, on one particular phone, it only offers me phones that were last used 5-20 days ago. My main phone, which I use constantly (we'll call it "daily driver"), and which I want to restore from, is not listed on this one phone.

Even though this one new phone (LG Leon) insists on only offering me old backups, I have tried it on other phones and the first one in the list is always daily driver and I can restore from that.

So, I guess the question is how does Google decide what backups to offer for restoration, and is there some way I can get it to offer me the same backups on the LG Leon as it is offering me on the other phones?

(I didn't post this in the LG Leon forum as I think this is really a general Android question.)