Yeah, I think using different sources and cutting them together wouldn't look good... maybe upscaling the film without special effects and re-build the effects would be best, but very time and money - consuming (they could do that, but...
).
I never thought about in which format all the short films were filmed. Is there a list/info which ones can really be transferred to 4K?
I think the AI upscaling looks like when you sharpen a jpeg too much and reduce the noise...not a big fan. But it would be okay-ish,
if there is really no other possibility and they didn't use the wrong tape in the first place.
But again I have to ask myself how can all these tapes be lost. I am a photographer and I always have back-ups of important shootings, raw files included. So in this case I would assume they have back-ups of back-ups of back-ups etc.
Not to defend the estate's actions, since we know they tend to follow the "whatever's cheapest/easiest" route, but there could be a number of reasons for not doing a proper film scan. Obviously the biggest one is time/money, and that's probably the reason here. Especially considering so many other artists have opted for the cheap and easy 4K upscale without much controversy (look at Janet for example). Going back to the film source and re-scanning/restoring to 4K is a timely and costly procedure; one I'd argue is
worth while for an artist that re-defined the music video art form, but also I can
kind of understand why you'd focus on only the most important/iconic videos.
Now, let's say they
wanted to do new film scans, it
is theoretically possible that the source is missing/hard to locate and these AI versions are stopgaps. In the case of THRILLER we know that work took quite some time, was initially done for the 3D conversion, and that some music exec had a 35mm print of the short (presumably the estate did too but based on the stories we heard about record keeping its entirely possible they didnt).
But let's now say they even DID find the original negatives to scan, the reality is this videos going to have a couple shots that simply will not exist in any form other than video -- namely those (at the time) groundbreaking digital effects. They were made in the early 90s and cannot simply just be "recreated" as some people assume (the software is likely obsolete, the original working files likely missing, and the source material for those shots may not even exist anymore to attempt to "rebuild" from scratch). You could do a close approximation, sure, but then people would be complaining that it's slightly different (technology has come a long way since then, but those effects truly were groundbreaking and required lots of manual adjustments - there's no way to simply do it again perfectly). The
only solution for those effects are to upscale those shots. The limitations are entirely technical.
Now, could you still intercut them with properly scanned footage? Absolutely. This isn't
entirely uncommon, especially with films of this era. There'd be a noticeable dip in quality, but considering most of the shorts are relatively VFX free, it really shouldn't be a huge deal.
I'm still holding out that we'll get a proper home video release of all the short films, properly scanned from the source, and with as little up-scaling as possible, being used only when absolutely necessary. But I'm not holding my breath... we still haven't got the HIStory Munich 3D release that's done and dusted and just sitting waiting to release. Not to mention when they uploaded Ghosts it wasn't the HD scan that's out there.
Is the AI upscale disappointing? Yeah. Is it an improvement over the terrible quality, compressed 480p versions we previously had, I'd say yes (barring the new censorship). Is this par for the course for this team? 100%
That's how history changes 
