You could be right about the JSA requirements. The reason they brought in the minimum income floor for UC was that there were lots of 'self employed online traders' selling bits and pieces and making hardly any money but would then qualify for substantial UC top ups.
So now after an initial period, you need to be making at least NMW for a prescribed number of hours.
But people will still get around it because if your online trading business doesn't work you can then move onto 'mobile beautician' aka doing your mates and sister's nails or dog walking, cleaning etc.
All different businesses so presumably allowed separate build up periods.