Years ago, like 40 or so years ago, the smells at a fabric store would instantly make my throat, head and chest hurt. Formaldehyde or something equally offensive. Pre-washing would be sensible in that case. But although new fabric still has an odor, it doesn't hurt me physically like it used to. For some folks, pre-washing may be a hold-over from days when the chemicals were stronger. If it caused you an asthma attack back then, it makes sense to try to avoid that.
I don't think I would ever buy pre-cuts if I had to wash them.
And, to me, it doesn't make sense to wash the big pieces and not wash the small ones. So I don't prewash.