I think "substantial" is doing a lot of heavy lifting in the sentence I quoted. For example, I’m not going to argue that aspects of the process haven’t improved, or that Claude 4.5 isn't better than GPT 4 at coding, but I still can’t trust any of the things to work on any modestly complex codebase without close supervision, and that is what I understood the broad argument to be about. It's completely irrelevant to me if they slay the benchmarks or make killer one-shot N-body demos, and it's marginally relevant that they have better context windows or now hallucinate 10% less often (in that they're more useful as tools, which I don't dispute at all), but if you want to claim that they're suddenly super-capable robot engineers that I can throw at any "substantial" problem, you have to bring evidence, because that's a claim that defies my day-to-day experience. They're just constantly so full of shit, and that hasn't changed, at all.
FWIW, this line of argument usually turns into a mott and bailey fallacy, where someone makes an outrageous claim (e.g. "models have recently gained the ability to operate independently as a senior engineer!"), and when challenged on the hyperbole, retreats to a more reasonable position ("Claude 4.5 is clearly better than GPT 3!"), but with the speculative caveat that "we don't know where things will be in N years". I'm not interested in that kind of speculation.