[irishcoffee]

The reddit explanation in the post addresses your question I believe. If someone is at a 28 or 29 a few "charity" points can be found in subjectively-graded tests.

[jameshart]

I think that really just reflects the fact that on subjectively graded tests the score really doesn’t have that many significant figures of accuracy. That a regrading can find 3 to 5 points by being more generous - or presumably take 3 to 5 off by being harsher - says that really you could save a lot of effort by treating the final grades as bucketing into 10 point bands and treating 25-35 as the actual cutoff.

[aesthesia]

Isn't that equivalent to just setting the passing threshold to 25, with the same incentives?

[jameshart]

… which is effectively what result this process seems to produce already.

[dvh]

If you grade individual questions, you don't know the total score.

[rvba]

The incentive to find the extra point would partially disappear.

[TeMPOraL]

Unfortunately this is the final exam from pre-university education. You can think of it as one's first educational degree, a step below bachelor's. It's expected - particularly by employers - that everyone should achieve it.