Question about mastered in 4k blu rays.

[Rottweiler30]

Ive just had an eye opener in another thread to learn that the remastered 1080p blurays of Back to the Future are apparently awful due to HDR to SDR conversion?

I thought HDR to SDR conversion was only an issue if you played back a UHD disc on a 1080p TV. I didnt realise that it also happens during the disc authoring process for standard blu rays?

Are all blurays mastered in 4k subjected to this extra process that gives yet another way for a disc to be sub par? A bit worried about all the blu rays I own from 4k scans in my collection that I havent watched yet.

Or if they are put through this process is it at least rare that the blurays look bad because of it?

How does it going wrong show itself?