It is new. It is fancy. It is not clear where HE/DP is being used, it depends if the code is written using the Swift toolkit, but even that has paths for exfiltration if used incorrectly. They claim they are using DP in Photos as stated in the article here:

https://machinelearning.apple.com/research/scenes-differenti...

But the fact remains they are looking at your pictures. I do not trust them for one fleeting fart in the wind on this. Think about it for a hot second: HE/DP allows you to perform operations on the data without knowing the data, but what if someone goofs an operation and it ends up returning the actual data?

Sorry, not buying it. Crypto is hard to get right, and when it is monetized like this for "new features", it is wildly unnecessary and exposes users to more risk.