I notice this but with inhibition. I find I do different kinds of coding, more creative and less rigid, when I have less inhibition. Good sleep is good for rigid code, bad sleep is good for creative problem solving and inhibition. I tend to be better on the phone on <6 hours of sleep as well. I think getting a full night's sleep leads to my prefrontax cortex functioning properly, which I find makes me rigid and anxious with all the threads I follow and things I predict. Without a good sleep, that is significantly inhibited, making it easier to go with the flow, on a call or writing code.