Add the old software version to the "Software Updates" page that shows each update

I know that. But as you say yourself: it's cumbersome to drill down one level for each car that got a new update just to find out which versions get the update on a preferred basis and which don't.

You misunderstand me. Each vehicle in the VIN detail (by build) page has a link that, when clicked on, displays the entire software update history for that car -- just like it does for your own. It does, however, require you to drill down a level... Yes, displaying a column with the immediately previous per-vehicle build would make for a quick scan, but not certain of the value...

This isn't so that I can see my own version history or that of a specific car, but so that when a new version rolls out one can see which cars get it.

The complete VIN software history is already available in the detail (by build) page.