JC Whitney catalogs used to carry add-on vacuum switches that would cut off power to the A/C compressor if the throttle vacuum reached a certain point during hard acceleration. Once the vacuum came back up, it switched the compressor back on.
In those days (30 years ago), it made a huge difference to click off the A/C for hard acceleration. With a car full of passengers and a trunk full of luggage, it wasn't unusual to have to shut off the A/C to make it up a steep grade.
I'm not sure I've ever noticed a click or RPM drain on my new MBs; maybe they're variable compressors tied to the ECU?