> Surprisingly, only a few people knew about the dir attribute in my interviews
No. Most of those few people who "knew" it are decent-to-good readers with enough context to figure it out, and in this particular case they probably recognized "ltr", then worked backward to get what "dir" means, and were confident enough about that guess to state it as fact. They did all this in less than a second, because, again, they're decent-to-good readers who had the right context for this particular task. If this had been a made-up attribute you'd have gotten nearly as many people who "knew" it, I guarantee.
This is closer to a web dev reading test than a direct test of knowledge. Which, again, might not actually be a crazy thing to administer.
I see this too often. A developer (usually more towards the junior end) who think they can just chug through any problem. Trying this, then that, then google, then that again. When, if they would just stop and think through the problem - and use their eyes - they would see the solution was there all along.
> Note that since our technical discussion is a conversation. I don’t expect a perfect answer from anyone. If I hear some right keywords, I know that the candidate knows the concept, and I try to push them in the right direction.
If I were being interviewed, I would probably say "yeah all those meta tags are metadata for various consumers. The apple related ones are probably for tailoring the page for display on apple devices"
Hopefully that's good enough, if I were doing the interview I wouldn't expect more than that.