Sticking Alternator Pulley or not!

After noticing that the alternator pulley was not turning and fearing another fanbelt snap, I tried to ease it off by spraying it with WD40 and turning it with a pair of grips. It remained very tight and when the engine was running it was screeching, after all this effort I suspected worn bearings (the fanbelt was not over tight and had been set with correct amount of flex).

Now I have removed the alternator and expected it to be tight to turn, no it was free as a bird with no sign of binding!

Now I am confused

Has anyone else experienced anything similar?

ps the car has done 110k miles but not sure if alternator is original.

whats the bottom pully like has it come apart ie middle and outer bit

Sorry Mark what do you mean when you say the 'bottom pulley' excuse my stupidity.

crank shaft pully thats at the bottom its a term used in the motor trade

No ive been out and checked it, it all seems to be in one piece.

does it only do it with the alternator belt on what about the P A S belt tensioner and doest it do it when the P A S belt is fitted