BS. Either is stealing and your attempt at rationalization does not make it something else. We just tolerate some things and level of tolerance varies greatly. There are bosses who would nail you to the wall should you take a pen with you and I also know bosses who would tolerate that $500 cake taken by PA.
I don't think it's as black and white, and I don't think the single dimension of "toleration" works to explain the complexity.
Consider napkins at a fast food restaurant. Nobody would say you're "stealing" if you take one napkin and use it to clean your hands after eating. On the other hand, most people would call it "stealing" or at least ethically wrong if you took all the napkins that were available, far more than what you need. In this case, there's more to our ethical intuition than just "stealing" vs "not stealing". Factors include how much you need the napkins, how much you deprive others of the napkins, whether or not the restaurant would be ok with your behavior, whether or not the behavior is a cultural norm, etc.
In case you did not know in some places employers install monitoring software and cameras and you can get your ass nailed just for that - stealing time. They call it different but one still gets fucked.
