I "refreshed" my 4.000 firmware using DJI Assistant 2, and uninstalled and reinstalled DJI GO 4, and now I have QuickShot. I'm not sure which step fixed it, but one of those did.
All good until the next firmware update - next weekend probably?
It's a shame DJI does such a poor job of documentation/instructions. No where (that I can find) have they published the specifics of the various QuickShot modes, such as How High will it go?, How Fast?, at what angle? How high/far do you need to be before you can activate it? ... etc.
They give us such limited info as to exactly how they work - their typical modus operandi. The only way to know for sure is repeated testing (in a very large wide-open space). --- OR by watching YouTube videos of other people who have already tested them.
They must be charged "per word" to translate Chinese into correct English for their manuals. And evidently paper is in very short supply in China, since all their documentation is printed in Font Size 4 on matchbook-sized booklets.