Whether BSA is ‘relevant’ depends on your career situation. If you’re going places then moving every couple of years can still be the norm unless you’re prepared to leave the family & commute. More stable careers are possible but you can’t guarantee that You won’t get posted ‘for service need’ if required.
I’d moved every couple of years and with the expectation of continuing to do so put my kids into boarding schools. As it turned out I remained stable for the remainder of their educations so with hindsight did I actually need it? No, but going back to the start had I asked the poster for a guarantee of stability would he have given me one? No again.
It’s an easy allowance to paint as ‘allowing nobby officers to send their kids to posh schools’ but it’s equally used by NCOs and the cost in lost retention would likely exceed the cost to the taxpayer. I have a friend in the army who has moved every posting of his career, including overseas multiple times. His kids would be massively affected by this but for BSA.
It seems to me that it’s a small price to pay to retain experienced people who would be lost otherwise. I don’t expect this kind of article from the DT, it’s more typical of the Sun/ Daily Mail.