If its so complicated you "finish late" if you start at 4pm?

Well, I think your tech screening process could use some work then.

There is something wrong if you can't finish a tech screen in an hour imo.

Not defending it, just mentioning why it might be that way at large corporations. Also note that it'll take the interviewer extra time to do their writeup afterwards, so it does amount to extra work on their part.

At smaller companies they'll probably have less bureaucracy, so they can make hiring decisions quicker with less paperwork. Also team members will care a great deal more, since they'll be personally working with the candidate.