Ok, my bad!
the problem arose from the fact that I have a library of styles that is in my assets folder
(I avoid keeping libraries in any program's native folder, so that with any upgrade/format/new pc I can have everything in one place, and not worrying that I might erase some library in any program's native folder)
"The golden rule: reference libraries, don't keep them in the program's folder"
It appears that layout was indeed syncing with the su folder, it's just that my library wasn't there.
(BTW: it would be a good thing for layout to automatically detect any referenced (favorite) libraries from sketchup)
Now, since you said "This results in damaging the link between the original scene in SketchUp and the viewport in LayOut." and I think I saw you saying again somewhere in the forum, may I ask how it is damaged?
The workflow I've set up so far is as follows: I use scenes only to define active sections (no camera, no style, no nothing, just the active section) and then I have a few styles, each with two variants: one with sections and one without. that way for example I can have an east elevation and just by changing the style it becomes an east section.
The reason I do this is because otherwise, just for a simple house I would need to make 12 or more scenes. but this way I only need to make as many scenes as my sections.
So far it has worked great and I haven't had a problem when changing styles. Is there some specific reason you don't advise it?