Probably, that's the point of it, however your smartphone becomes a very dumbphone in lockdown mode, intentionally to reduce attack surface. It's only really practical if you just need a dumb phone system endpoint to send and receive SMS and PSTN calls and check the time.
I keep my phone in lockdown mode and haven’t noticed too many problems day-to-day.
A few minor inconveniences (webGL doesn’t work, the magic automatic code from SMS keyboard integration is gone, etc.) but overall the phone is still a smart phone.