Maybe 10 years ago I interviewed both for Netflix and Facebook.

At Netflix, I used a state machine library to handle the project they gave me. Got rejected because I didn't show I knew raw JavaScript enough.

At Facebook, I wrote a calendar dropdown from scratch. Got rejected because I should have used a library.

Interviews sometimes is just a lottery...

Yes I know both companies should have set the expectation, but you can set the expectation for EVERYTHING, otherwise you give candidates all the answers you're expecting. There's always going to be some chaos due to the huge number of variables.