Depends on what you mean by overkill. Effort? Then yes. Security? Then no. If the data is there but inaccessible you can be detained until it is. If the data isn't there to begin with, there's no reason to detain you.

I'd call that more of an effectiveness thing than overkill. And it would be possible for an app to not unlock the phone until it enters a certain geofence, like the hotel.

That wouldn't work in the UK, where not providing plain text when asked carries a prison sentence.

The app wouldn't accept a password, just a time and location to unlock. I'm not sure if that's better, but it technically sidesteps that issue.

I said plain text, not password. And it doesn't side-step anything because when you're in front of a judge and explain why you cannot provide plain text, they'll take your phone from you, get it to the location you tell them, and if none of that yields plain text, you go to jail. Two years, they give you for that.

Who has gotten two years for that and lost the appeals?

That only applies if there's a court order to reveal the data, not at random border checks.

I think it reads better if "overkill" above is seen as an imperative verb, as in "I suggest you overkill." :)