Until someone invents a teleporter, walking to do a job task constitutes work.
If the company does not want Dilbert to walk, then they should make all his task on one place. Unless of course PHB wants to volunteer to carry Dilbert on his back while Dilbert works on the large screen smartphone.
Dilbert doesn't understand. Stealing from the company is not just a way of life, it is a basic survival tool. The company takes all your time whether they use it or not. Every minute you steal back is yours and yours alone to spend as you see fit. Which certainly includes the privilege of wasting it to bug the PHB.
Not working while walking to and from the coffee machine is probably only rated a misdemeanor. However, I suspect Dilbert does not even use his phone to get work done while driving to work or eating dinner, and that may be a firing offence.