There were some companies like Microsoft who were starting to become known for being more intense, but I never came across that.
It wasn't until the mid-aughts that I started to see brain teasers, "real" whiteboarding, and other aspects that started to bleed into standard interviews.
Perhaps the turning point was Jim McCarthy's "beware of a guy in a room", which he meant both figuratively and literally, leading to a transition away from solo or shared offices or even cubicles for software engineers and toward open-plan arrangements. I think that his wisdom led first Microsoft, then the rest of the industry, to treat software engineers not as the darling whiz kids they were in the past, but more a cohort to be closely watched and controlled, as the company is risking a lot on them.
interviews at twitter back in 2010 were 6 hours and that was true even for me when we had an agreement to acquire my company pending the success of those interviews. at the time they had a lot of ex-googlers and they were setup similarly.