I put tech interviews down fifty/fifty to "We don't know any better way of doing this" and "The unavoidable reality is that if a position is advertised openly then 98% of candidates are screamingly inappropriate for it and after applying a few filters to the resume we've gotten that to a more manageable 90% or so for interviews."
Happily, there is a simple opt out mechanism. There are two ways to get into any company: through HR and the resume -> interview -> offer process, and the other way. (Convince a decisionmaker within the company that you, specifically, are the answer to their prayers. Get hired. Skip slush pile.)
Pick door number two. If you get your jollies off of sorting linked lists you can do so after having received the moral equivalent of an offer (which should decrease the stress to the point where you can successfully sort a linked list).
I consider the existence of door #2 a red flag. If decision makers who are likely not technical themselves are making that kind of decision about technical hires, odds are that they are going to make some very bad hires that I won't like living with.
That's not to say that there aren't a lot of companies where your advice works. But I'd prefer to work for the companies where it doesn't.
Even assuming that you're not a bad hire, it can still be a bad idea to allow this. If the decision makers can go over the heads of the people who are in charge of technical hiring and force them to take on someone they haven't vetted then that's just going to cause resentment.
I don't mind skipping HR so much. But skipping the technical-vetting step is bad. If your hiring-committee doesn't make good decisions, that's a separate problem that you should solve without just starting to ignore them.
I would suspect that "door #2" is most useful in the (more common at large companies than small?) case where a technical lead of some sort has a position on their team they want to fill, and HR is a barrier between them and the engineer(s) they want to bring on board.
I've picked door number two consistently throughout my career. It's more effective and much more meaningful to establish a relationship with decision makers from the get go.
However, it addresses the problem only from the point of view of the hiree. For companies looking to hire people, the typical interview process is equally a problem.
I think the "dating" process described by the OP sounds like a good solution for the hiring company. It's also a good signal to the employee that the company is serious about hiring the best, using the best methods.
The "dating" process only works when both parties are available. If the candidate currently has a job asking them to take time off (or worse, quit without a guaranteed offer) is asking a lot.
Happily, there is a simple opt out mechanism. There are two ways to get into any company: through HR and the resume -> interview -> offer process, and the other way. (Convince a decisionmaker within the company that you, specifically, are the answer to their prayers. Get hired. Skip slush pile.)
Pick door number two. If you get your jollies off of sorting linked lists you can do so after having received the moral equivalent of an offer (which should decrease the stress to the point where you can successfully sort a linked list).