TLDR: It's okay to take naps while working from home
Brief:
I feel that there is nothing wrong with taking afternoon naps while working from home. Mainly because after taking rest for a couple of hours my mind is re-energised and I am able to pull off quite a lot of work in much lesser time after waking up and my overall productivity for the day roughly remains same.
This is mainly because if I end up staying awake even when I am tired and sleepy there is not much productive work done even if my number of hours online increase.
And if a company has strict measures set for calculating the number of hour employee stays online while working from home then it will actually reduce overall employee productivity rather than having any kind of actual benefits.