95 Safari. Why does my AC compressor cycle on and off when I move control lever to defrost?

Because dry air can defrost wet foggy windshields faster than wet damp air--- all modern vehicles are designed to do this...

this is when AC is not on.

this is when AC is not on.

Correct. The compressor will run to help dehumidify the intake air for more effective defrosting. Many cars since the 1970s have done that.