any idea of a ballpark # of boards of that ilk?

Another one - a rash of alum. electrolytics which were Not "low ESR" (equivalent series resistance, for the non electron heads) -- as used in ubiquitous/cheap PSs and on mobos, as added filtering for the DC-DC inverter, lo-Volt/hi-Current CPUS du jour.

One would expect the increased resistance (over proper caps) to result in increased ripple, doing all the bad things that ripple does - like digital glitches.

I don't recall if they were mismarked "low ESR", but think not - believe you could read the label to see if the "Low ESR" stripe was absent.

Seen any of those?