GF can only squirt but not contract

Hi my girlfriend (27) can only squirt (from clitoral stimulation) but there are no rhythmic contractions. Fit feels like she has involuntary contraction but it's just a single long contraction of her whole lower body. For me it's also nice but I wonder if she misses out. She enjoys it and it builds up like normal and she feels relief after. She thought this is what the average orgasm is like and didn't even others contract rhythmically. I told her "you have these muscles, can't you contract them voluntarily?" And we found she never learned to control them. We tried around a bit, I gave her feedback and finally she managed to control them, lol. But it did not change her orgasms. Actually pretty expected to me: she trained this subconsciously other way for years and is not going to replace it suddenly.

Is this something usual? Anyone managed to relearn this?