I think of memory, and lookups in humans similar to L1/L2 cache, RAM, Network and Disk.
Knowing stuff cold makes you incredibly fast. Doing a lookup of a problem you've solved in a personal project / elsewhere you have the code for is also very quick, but not as much. Having to perform lookups is akin to having to go out to RAM. Having to ask a coworker is slower still. And the slowest is having to learn something entirely from the ground up before you can process what you are seeing.
It all makes a difference to your throughput, and as you say your creativity!
Knowing stuff cold makes you incredibly fast. Doing a lookup of a problem you've solved in a personal project / elsewhere you have the code for is also very quick, but not as much. Having to perform lookups is akin to having to go out to RAM. Having to ask a coworker is slower still. And the slowest is having to learn something entirely from the ground up before you can process what you are seeing.
It all makes a difference to your throughput, and as you say your creativity!