I'm not sure I would measure LLMs on recommending a fairly obscure and rather new spec that isn't even fully supported by e.g. Chrome. That's a leap that I, a human, wouldn't have made either.
For an LLM, I’d expect it to be similar. It can recall the stuff it’s seen thousands of times, but has a hard time recalling the niche/underdocumented stuff that it’s seen just a dozen times.
The human brain isn't a statistical aggregator. If you see a psychologically socking thing once in your lifetime, you might remember it even after dementia hits when you're old.
On the other hand, you pass by hundrends of shops every day and receive the data signal of their signs over and over and over, yet you remember nothing.
You remeber stuff you pay attention to (for whatever reason)
I am fine with this, but let's be clear about what we're expecting
Certainly a majority of people don't know this. What we're really asking is whether an LLM is expected to more than (or as much as) the average domain expert.