Some of my shastas get a good 5 feet tall. It depends on the weather and the soil and so forth. So they probably were shastas.

Sierra

'Alaska' is my tallest white one too, I would say its about 4 feet right now.

Last year I had several transplanted shastas (unknown variety) that reached 5 ft. But it was an unusual year - I had many extra tall plants. This year they are at most 3 1/2 ft