Personally, I am more concerned about the tr case than arbitrary elements. Probably I should have started this topic with a narrower focus, but it's too late now. The tr case is a real limitation that I have encountered on numerous occasions, whereas linking arbitrary elements is more of a nice-to-have.
That said, my justification for allowing linking on arbitrary elements is the improved developer ergonomics of not needing to add wrapping anchor elements everywhere. So, in this case I can't present use-cases, as it is a proposed improvement to an existing feature — e.g. linking.
The improvement might sound slight, but I think it would be quite considerable. Firstly, it is a chore that needs to be done frequently when developing a web app. So often in fact, that I suspect many devs do it mostly without thinking, and without considering the amount of time they could save if it were as easy as simply adding a href attribute. Even a small optimisation can bring about considerable savings when applied to a common task, and may justify effort that would be
It is not just a case of adding a bit of extra markup: When the anchors are added within a layout such as flexbox, additional CSS is needed to fix-up the layout, often requiring nested flexboxes. Replacing the existing container element entirely with the anchor may not be possible if it has semantic meaning, or is a web component.