I can vouch this is a terrible process. Unless you interview ONLY at Google, you almost always won't work there. When you are actively looking, you usually want all your interviews to be close to each other (within weeks) to evaluate offers and make the best decision.

It's extremely unhelpful if one company is still in the "screening" phase because they take months to progress, while others are already extending offers. The options then are that you wait and risk letting go of other offers, let go of Google, or join a new company and leave within months. All of these options look terrible to me.