I had installed bitcoin-wallet app on an old phone a couple of years ago, just out of curiosity about bitcoin. I obtained somehow a teeny amount of bitcoin, .0017xxxx anyway, I installed the app on a new phone, and exported/imported. This all worked fine.
I am just curious about what then happened... on the new one after the import, it initially said something to the effect of "recreating (resyncing?) 30 months of history" or something. And very very slowly the number of months went down and eventually got done, taking maybe a day. I did notice the phone was pretty warm :-) Afterward, I had to chuckle because I just happened to notice the phone said it had used 50GB of data that day (!)
Is that all normal? What was it doing all that time? Is it necessary?