The 6.3% would appear to be bite people on middle incomes, so it really depends on what you are doing.
If you graduate with £60k of debts, then if you are on less than £25k you don't pay anything and the loan never changes in value
Above that it varies, but if you are progressing to a lucrative job then you will be penalised.
The RPI interest is £1980, and £1980 / 9% (repayment rate) = £22,000, and with a £25k repayment threshold that means that if your salary will never go above the equivalent of £47k (as the repayment threshold is uprated with wages), then more-or-less you will never repay the loan (disregarding of course that RPI will vary from year to year)
The point comes that if your wages are on a pathway to a higher level, then you will be racking up fairly big debts that the government will want back off you in the future. For instance, if you earn £45k as a graduate then your debts are in fact INCREASING because it's rpi + 3%. So your debt is compounding at 3% real terms, and as a future lawyer on, say, £150k, you will be paying back a rather expensive debt, in full.
The point here is that the penalty is only incurred IF you are a future very high earner, AND you are currently a high earner. So if your graduate salary is £45k in a high-flying profession, then:
(a) rich person, no student loan - can look at investments, buying a house, etc.
(b) average person, full student loan - should pay off their student loan
The result of this of course is that, say, the City lawyer from a rich family at 40 has a much fancier house than the one from a normal family.
It's hard, of course, to shed a tear for a graduate on £45k - if you are single and have a takehome of £34k, well the government would be happy if you stuck £15k into paying off your student loan.
But clearly that money that they are encouraging to repay has an opportunity cost, be it investments, private school for your own kids, or whatever. And clearly some part of that could have future effects in for example concentrating privilege (i.e. the very highest paying jobs) in the hands of those who already have money.
But it's not what the BBC article says, at all.