Unfortunately, many people see their student loans as something they don't have to pay back.]Technically, if they satisfy certain criteria within the T&C's that is correct. However, modifying your lifestyle to ensure you always fall below the repayment threshold is fraudulent in my opinion and not really any different to tax evasion.
I think that's a bit strong. I don't think that modifying your lifestyle in that way is fraudulent because then you live a life you much sustain on payments that are indeed below that threshold and it becomes an informed financial decision (albeit an arguably immoral one).
If I were a higher rate tax payer, I could opt to put the proportion of my taxable income that would fall within that higher rate bracket in my pension pot (before tax is deducted via PAYE), thereby putting the gross funds into my pension pot and only being taxed at the lower rate on my annuity. If I were to do that, I would effectively dodge the higher rate bracket. Similarly, I do not think that is fraudulent, but an informed decision.
Of course, claiming that you are earning X to HMRC or creditors when you are in fact earning Y, is bona fide fraud.