Clutched Alternator?

Recently I have noticed that my volt gauge on my truck reads about 12 volts if I am accelerating or cruising. Once I let off the gas and coast I notice it jumps up to 15 volts. It is extremely consistent so it made me think that Toyota is using a clutched alternator similar to an AC compressor where they are only engaging it when the truck is coasting since the injectors are shut off and the truck is not using any fuel and disengages when the engine is working to reduce the drag on the engine and improve efficiency.
Am I accurate with my hypothesis or is there something wrong with my truck?

I'm not up to date on the latest tech so forgive me if this is a known thing.

 

It’s a normal alternator and not clutched. The ECM just switches it off so there’s very little resistance from the alternator. Nearly all manufacturers do this now. Look up smart alternators.

 

This. Its a pain in the ass on my 2014 F150 because as soon as the battery gets even slightly old and doesn’t hold voltage as well, the truck wont keep the interior electronics on with the key in run but engine off.

Ive got a 5-6 year old Odessey AGM battery that still cranks like a monster but the pcm thinks its dead and turns it off.

 

It's turning off to save fuel consumption.

Some alternators do have clutch pulleys though, usually sports cars so the belt doesnt slip when you shift gears at high rpm. Not sure if the third gen has one, i doubt it.