I agree with you up to a point. Changes in new printings that don't make it to errata are problematic because they might be newly introduced issues. To use an M&M example, the pocket version of the 2e Core book had fixes accumulated over the years. It also had a blatant error in the Size tables. A more real-world issue, look at how many variant Bibles came out with an editing error from the "Thou shalt commit adultery" one to the 5th century gospel where Jesus's ancestry got doubled
That said, most of the discussion is less about the change to round up the discount, which is pretty clear, but rather where the clause applies. That one is ambiguous. And, as many people, including yourself, have said, it's just a point or two at most.
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