Following T143151 I had a brief look are there any other parts of the page that should be updated when diff is reloaded, e.g. they should refer to another revision.

It seems that in the side panel at least following links are revision-dependent:

• permanent link
• download as PDF
• download as plaint text

All rely on the "oldid".

So it looks the side panel should be updated as well.
But this still might not be enough. There might be more core things relying on the particular revision, and extensions might be adding their bits into the equation.

On the other hand, as we would now be updating almost whole "main" part of the page below the revision slider, the navigation bar, and the side panel, there is not that many things left, so maybe that would be enough.