Yup. Apple's tech support insisted that the reason my iPhone 6 (not a 6s) shut off at 30-40% was due to a software issue, not a battery issue. They suggested I not only wipe my phone, but set it up as a brand new device. It's insane that this is the only way to fix something they claim to know is a software issue.
This is their default response to everything. Once you go through that step (and they maybe grab diagnostics to determine you actually started as new), they will actually push to resolve your issue. It's easy to recover from this w/ iTunes or iCloud device backups, so a moderately painless hoop to jump through.
I can backup, wipe my device, do the test, pull the debug logs, and restore from backup in an hour or so. iTunes and iCloud make it really easy to do this. It's just not cost effective for Apple to treat every case as a special snowflake if nuking from orbit fixes the issue. It sucks, but it's not like you'll get support from anywhere else.
