It's better to have a lax SEAS system and help those who actually need it (plus more who might not), rather than having a strict SEAS system where some of those who actually need it miss out. Which is what happens currently, it's never going to be an even playing field no matter what you do, but at least accounting for some of the discrepancy allows those who do have the potential but weren't able to utilise it during year 12 due to some circumstances, to go on and be able to give uni a good shot on a more level playing field. If anything, most of those I know who got SEAS are those who go above what is needed and do well at uni (anecdotal evidence, but still).
EDIT: Spelling.