Not sure what you mean here, but my watch unlocks my phone anytime faceID fails (usually because of my hat) or anytime pin is required for security reasons.
Now if you mean with someone else trying to unlock my phone, then no, the watch will not unlock it. My wife and I have tried this extensively.
No. I mean if the phone is locked to require passcode, which happens at a minimum of every 6.5 days, or every time that you restart the phone, the watch cannot unlock it. Even if you have mask-wearing unlock with Apple Watch turned on.
As an example, if you squeeze the side button and vol up until the emergency screen comes up, then cancel, you cannot unlock with Face ID, Touch ID, or the Apple Watch. You must enter the passcode.
Well if you hand your phone to a stranger unlocked you are just asking for trouble

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Well, yeah, I agree. It's extremely rare when I allow this to happen myself, but I'm generally not all that wild about having my photo taken anyway.
But it doesn't need to be unlocked - you can swipe left from the Lock Screen, or long-press the camera icon on the Lock Screen. The phone can still be locked; somebody who wants to try this with you can still lock you out of Face ID or Touch ID by the long-press of the side button and Vol Up. When they hand the phone back, you need to unlock with passcode. These people work in teams, so they either shoulder-surf you unlocking the phone, or even video while you aren't looking, so that if they can steal the phone, they can unlock it immediately, then lock you out of your Apple ID.