Well, I actually work for a FAANG company (not going to say which one), and I didn't have to spend hours a day for months to do so; granted, I'm a bit of a math/theory junky.

EDIT: Also, at least with the Hackerrank for hours a day, it's not for any specific company. Getting good at these problems is useful for getting a job at virtually any big company. Contrast this to the take-home project, where (in order to make sure you don't just copypaste someone else's from the internet), they make these things kind of specific, making the transferability to other things substantially less likely.