No, that was mostly just snobbery. English musicians in those days tended to play for the benefit of the dancers rather than to show off. Scottish players of Jimmy Shand's generation come in for similarly snide criticism. They could play fast if they felt like it, but they didn't; because that wasn't what the music was for.

Kaleea isn't talking nonsense; you can only arrive at a proper understanding of a dance tune by accepting that it was made to do a job. It was designed for a purpose. Ignore that, and you may end up with a superficially impressive performance piece, but it will have lost its soul. True elegance, and beauty, retains its original functionality. Without that functionality, it risks becoming effete and sterile; like a beautifully ornamented false pocket that you can't put anything in.