Indeed it does, however what the "proof" is has changed. In terms of sitting down and doing a full, deep review, tracing every path validating every line etc. Then for sure, nothing has changed.
However, at least in my experience, pre LLM those reviews were not EVERY CASE there were many times I elided parts of a deep review because i saw markers in the code that to me showed competency, care etc. With those markers there are certain failure conditions that can be deemed very unlikely to exist and therefore the checks can be skipped. Is that ALWAYS the correct assumption? Absolutely not but the more experienced you are the less false positives you get.
LLMs make those markers MUCH harder to spot, so you have to fall back to doing a FULL indepth review no matter what. You have to eat ALL the pudding so to speak.
For people that relied on maybe tasting a bit of the pudding then assuming based on the taste the rest of the pudding probably tastes the same its rather jarring and exhausting to now have to eat all of it all the time.
That was never proof in the first place.
If anything, someone basing their trust in a submission on anything other than the code itself is far more concerning and trust-damaging to me than if the submitter has used an LLM.
I mean, it's not necessarily HARD proof but it has been a reliable enough way to figure out which corners to cut. You can of course say that no corners should ever be cut and while that is true in an ideal sense. In the real world things always get fuzzy.
Maybe the death of cutting corners is a good thing overall for output quality. Its certainly exhausting on the people tasked with doing the reviews however.
Ultimately I don't think the heuristics would change all that much, though. If every time you review a person's PR, almost everything is great, they are either not using AI or they are vetting what the AI writes themselves, so you can trust them as you did before. It may just take some more PRs until that's apparent. Those who submit unvetted slop will have to fix a lot of things, and you can crank up the heat on them until they do better, if they can. (The "if they can" is what I'm most worried about.)
LLMs are a tool, just like any number of tools that are used by developers in modern software development. If a dev doesn’t use the tool properly, don’t trust them. If they do, trust them. The way to assess if they use it properly is in the code they produce.
Your premise is just fundamentally flawed. Before LLMs, the proof of a quality dev was in the pudding. After LLMs, the proof of a quality dev remains in the pudding.