I would consider any device that's been through an inspection as potentially compromised as they could theoretically install a backdoor and access ur data later.
Maybe just using some kind of a burner phone is better.
If your adversary is the Mossad, or some equivalent thereof, they are going to do Mossad things to you, and you're going to die and there's nothing that you can do about it.
Call me a stoic or a fatalist or an idiot, but this is not something I'm concerned about when I'm crossing a border.
That's a bit hyperbolic. An institution like the Mossad has literally thousands if not millions of "adversaries". They don't kill all of them. They probably kill less than 1% of them.
There's plenty of downside to killing someone. E.g. in 2010 the Mossad horribly botched an assassination: http://www.dailymail.co.uk/news/article-1261435/How-Mossad-b...
If even 1% of their assassinations went that badly, the PR fallout would be devastating. I'm sure they're quite selective over who is "going to die".
Call me a stoic or a fatalist or an idiot, but this is not something I'm concerned about when I'm crossing a border.
There's a 100x greater chance, or maybe a 1,000,000x greater chance that the Mossad (or equivalent) compromise your phone than decide to kill you.
You don't own the baseband firmware, therefore do not trust the device.
The same is true of your desktop and likely router gear, but many of those at least require brief physical access to enable (however there's also in transit or baked in at the factory).
If you want a truly secure device demand fully open.
What I'm more worried about is my data being accessed as part of yet another mass surveillance program. I'm not saying that is not already possible with other means, but I would certainly not want to make their job easier.