[FooBarBizBazz]

I agree that it's weirdly euphemistic Californianese.

Two we can translate, I think:

"stable user experience" = "doesn't crash"

"responsive user experience" = "isn't laggy or slow"

It'd be nice if they just said what they meant like normal human beings, but both of those are reasonable requirements

(We can pick apart why they talk like that -- it's about implying that everything stems from their "care" for users; it's to seize moral high ground, but of course the "care" is Focaultian. I digress.)

But what's the third one? "engaging user experience" = "not boring" = "holds users attention" = "entertains users". That doesn't seem like a reasonable expectation, and in fact could be called the problem with smartphones -- everything is designed to be addictive. Is a hammer engaging? That's not the point; it's useful sometimes.