Yield is so complicated that one can't know truly without having actual data we are all doing guesswork
Here is my occam's razor's guess: yields are crap, and clearly it's not "just" parametric here.
Any potential external customer will demand to see actual data and get it, now they won't leak it as it will be under NDA, but them not taking it up speaks volumes. So who are Intel trying to deceive here? Can see only one target: the markets, ie: shareholders. Don't know how is that legal, but under current admin anything goes.
That doesn't mean they're bad or not improving.
It means they are bad, which in weasel words is "not where I'd like them to be". Are they improving? Most likely, but we don't know how fast, but if it was fast he'd say when they will get "to where I'd like them to be".