You might be able to persuade me that "any felony conviction" is too broad and only certain kinds of felonies should be excluded.

I think you hit the nail right on the head. The article even notes for this particular program:

Inmates convicted of crimes categorised as "serious" or "violent" felonies are not eligible, says Bill Sessa, a spokesman for the state's department of corrections and rehabilitation (CDCR). That rules out those convicted of murder, kidnap, rape and other sex crimes, violent assault, and - unsurprisingly - arson.

They didn't really say what these particular inmates were convicted of, or if they were even felons, but there are plenty of crimes in the US that are treated way more severely than they should, and in some cases shouldn't even be considered crimes at all.