I've always assumed it was a name for a clever way to improve on limitations of simple bang-bang control with on-off sensors and actuators plus some 7400 series

I've always assumed it was a name for a clever way to improve on limitations of simple bang-bang control with on-off sensors and actuators plus some 7400 series-type logic. Nowadays you can have an STM8 with two dozen 10 or 12-bit ADCs and enough grunt to do hundreds of PID loops at once for 10 cents.