I've seen an early alpha version of GP during the Scratch conference of 2016 (the 2017 conference is wrapping up tomorrow), and it worked awesomely, like a supercharged version of Scratch. A fun thing about it is that it features a very small VM, and the rest of the interface and blocks are written in GP itself, and can be readily inspected and modified.
They're rightfully waiting until they think things are ready to show. Danger of showing early is a recent memory in computing history (see Jobs / PARC visit)
From what I've heard of the Jobs/PARC visit I don't think I'd characterize it that way. In Walter Isaacson's "The Innovators" he says that Xerox had taken an ownership stake in Apple and some higher-ups decided to give them valuable tech.
You're right and my comment made it seem like everyone has some grudge or something. I think in general the PARC community was weary that the takeaways would be centered around how computers, GUI, etc. were great ways of doing old things better (accounting, reading text, etc) instead of being captivated by computing as a medium for thinking. This happened with print, as Alan has discussed in some of his talks. The first 100 years of print was used to print and distributed religious text and it took a while before ideas that could probably only sprout in the print medium were invented (physics, calculus, some philosophies, etc). To some degree, I think some people feel like we're still in the "use print for spreading religious text" phase (or the "film is a great way of recording & distributing plays" phase.
