[Oldtimer]

...The primary fan does not kick on until the needle goes to nearly 3/4. The primary fan will turn on with AC/Defrost.

Neither fan will turn on if I unplug the harness at the temp sensor in the water pump. ...

The primary fan is performing as it should.

As others have have suggested, try disconnecting the ECT with the engine running. They should turn on within 10 secs.

In practise the secondary is very rarely known to turn on during normal usage.