It’s a risk. But it also takes a few hours to restore from backup and there’s a bunch of things that (sensibly) don’t restore and require manual setup.
I know Apple will never ask for your passcode but in the case of a repair shop that promises 15 minute service it’s kinda necessary unless you want it to take far longer and annoy them.
Ultimately with it locked down with screentime the only personal data I had an issue with was iCloud Keychain. Honestly I don’t know why Apple lets children access the full settings anyway. It would be trivial to add a screen time restriction for all features of settings except the screentime pane.
I wiped mine, but then a couple of hours before my appointment for a battery replacement they called and said due to heavy snow the techs could not get, and gave me a new appointment a couple of days later.
I didn't want to fully restore the phone for just a couple of days, so just set it up with a temporary passcode and signed in to an Apple ID I normally do not use [1], so that I could use it for that couple of days without things asking me to sign in.
After the battery replacement I then wiped it and restored from a backup under my normal Apple ID.
This mostly worked, except it messed up my Longest Move Streak with my Apple Watch. I'm not sure if this was just due to the wiping the phone part, or the having the phone on a different Apple ID than the watch for a couple days, or something else.
What the Fitness app tells me about the streak now is just weird.
The streak started on 2019-05-07 and I've not missed a day since then. The battery replacement was on 2022-12-21.
When I checked the streak in Fitness on 2023-02-04 it told me that:
My longest streak was 39 days ending 2023-02-03
My current streak was 1368 days
Note that it is reporting a longest streak that is entirely within what it is reporting is my current streak.
17 days later, 2023-02-21, it was reporting:
My longest streak was 41 days ending on 2023-02-20
My current streak was 1385 days
Note that when it thinks that the longest streak started was sometime during the previous longest streak, so that makes no sense.
A few months later, 2023-09-23, it was:
My longest streak was 37 days ending on 2023-09-23
My current streak was 1600 days
I hadn't checked between that last and now. Checking now, on 2024-01-22, I get:
My longest streak was 1710 days ending on 2024-01-11
My current streak is 1720 days
That's better in that now it thinks the longest streak and current streak started at the same time, which is correct. But it still has the longest streak in the interior of the current streak which should not be possible.
[1] I've got two Apple IDs because originally you couldn't use the same account for iTunes and their cloud service, and so everyone who wanted to use both had to have two accounts. Later they made it so one account could use both.
I know Apple will never ask for your passcode but in the case of a repair shop that promises 15 minute service it’s kinda necessary unless you want it to take far longer and annoy them.
Ultimately with it locked down with screentime the only personal data I had an issue with was iCloud Keychain. Honestly I don’t know why Apple lets children access the full settings anyway. It would be trivial to add a screen time restriction for all features of settings except the screentime pane.