They are not the same which is why they are two different words. For example, memorising first 1000 prime numbers is not same as knowing prime numbers. The former person will not be able to figure out 1001st prime number because it's not in their memory bank but the later can calculate it. Sure it takes time to calculate but it's not impossible.

Now, I'm not belittling memorisation. A baseline memory is needed otherwise one'll be wasting time and energy figuring out everything from first principles all the time. This is akin to rainbow tables saving time. But as with all things in life finding right balance is key. As you pointed out, it's useful to memorise things at work to save time and energy.