1st Tier schools a Bachelor's degree holder has most of the fundamentals of mathematics within computer science. Complexity of algorithms, complexity of operations on various data structures, models of computation, problems that can be solved with different models, etc..
20 years on from going to school it took me a long time to figure out a lot of schools don't cover almost all of that until you're working on a Master's degree or Ph. D. It's really surprising.
I think some of CS questions in interviews are because the degrees are so variable. I don't think this is a problem when you're hiring a Mechanical Engineer or a Civil Engineer who is licensed. All the schools need to teach to a uniform enough standard that their graduates can pass the licensing requirements.
CS is a mess. The Top Tier schools seem like they may be so much better that a Bachelor's degree is worth more than a Master's degree from other places.
I think it's hovering around medicine. Where there is a seemingly art form to deal with the realities of our too complex biology.
And since that became the standard from the beginning, it's what remains now.