Sounds very like an instructor at Lasham I had many years ago.
Just before sending me solo, he pulled the cable at 900' and then kept the stick BACK with a boot of left rudder! It felt as if we went beyond the vertical before spinning down. Leveled out downwind at about 400', easy circuit and then went solo on the next launch.
As you can surmise, it left an indelible impression!
FBW