Then its working. Big companies love it when people spend time studying for their interview process. It shows commitment and means that person will feel like they "earned" that job, and should stay longer. This reduces churn, which is the thing they screening out the most. To the big tech companies, this isnt a problem, its a sign of success.

Think how whiny this sounds to any law firm/medical practice. People spend years studying/preparing/working for free to get an internship. And yet, most software devs are still payed better.