I think it'd be really fucking impressive if someone could discuss the ins and outs of systems they've used, likes and dislikes, taking conversational questions about it that they don't know about in advance, without setting off any alarms, while not actually knowing anything. That'd be wild.

I think a lot of the whiteboarding/leetcode stuff is just hazing, a desire for "standard" processes (every candidate has a different background, so a well-done conversational interview will differ a ton per-candidate), as a bit of a time-filler ("that's right [C-suite person who's asking questions] we have very rigorous hiring, look, it takes six hours, and see all these steps! Only getting the best of the best, I assure you."), and because if it's scripted you can have mid-level devs do it—poorly, for the most part, since conducting a good whiteboard/leetcode interview is possible, so far as that goes, but it's not easy and requires serious people skills, which is a big part of where places go wrong I think, and also tends to make it look so non-cookie-cutter that if you squint it's not really that much more "standardized" than the conversational version.

I think this is exactly right.

Sure, it's unlikely someone will be totally clueless who can talk the ins and outs of a project. Let me put it another way. If we put all the engineers I've managed/lead throughout the years through your interview process, you would probably filter out the one or two who were bad, but you would not always select the strongest engineers. You'd select the strong engineers who were confident, gregarious, and articulate, and leave out the ones who are humble, shy, embarassed by their accents, not used to bragging about themselves or articulating the details of past projects.

Talking about those things is a learned skill just like writing on a whitebaord. Hence why good companeis that do whiteboarding interviews also have traditional rounds. You want to give candidates multiple avenues to shine.

Not at all! My job as a skilled manager is to look beyond people who are outgoing and help people who are shy get comfortable during the interview. I've become very good at this and have trained other managers to do the same.

A casual conversation where someone is purposefully trying to put you at ease is going to be more effective at seeing someone's true skill over a whiteboard every time.

There are also a bunch of very senior people that won't play interview games at all. Especially when they're an internal referral. If I refer someone to get hired, I make absolute sure that they are not put through a technical hazing ringer. I've seen senior people who were heavily recruited walk the instant they're put into "the process" under the very sound logic of: "You wanted me to work here, so why are you making this difficult?"