Okay so after hours of speaking to a couple of Xbox Reps, it's clear that this is a more complicated issue than they had realised.
Here's what Xbox and I know for sure.
This is a back-end issue which when installing a Game, provides a one second executuble(this would be the Microsoft Visual code).
I tested numerous Games. Some seem to "need" this file. Whereas others. For eg Snowrunners and Visage. Install instantly and do not require any additonal file.
So. It's clear that this is NOT. I REPEAT. This is NOT an Insider App issue. Nor do you have to reset your PC or any of that extreme advice that people have suggested.
As we proved earlier, specific Games that don't recquire this code, download and install instantly. I tested it with Forza Horizon 5 with the new DLC. Absolutely no issues.
This is a back-end issue that Microsoft/Xbox have to fix.
I would not be recommending deleting apps/changing registry information or any of that. There is no need.
Resetting/Reparing the Windows Store/Xbox App does not work. As confirmed by one of the Xbox reps, being an Insider does not include any different data when installing/downloading a Game.
So be patient and I'm sure there will be a fix for both Microsoft Store and Xbox App soon. Hang in there.