I really don’t think this is the case and it really doesn’t match my personal experience. Especially under their true name, people behave as they would talking face to face.
You see, it's more damaging for you to be an a-hole in person in the (open) office because then everyone can see and hear you and know who you really are as a person, but in chats you can be as dickish and as dismissive as you like and nobody else, especially your boss will be the wiser thinking still that you're a great guy.
This behavior is more difficult to pull off in the office where everyone can see what you're up to and your boss can come up to you saying "hey Anton, can you please stop playing World of Tanks and help Joe solve that issue?" versus WFH where Anton can paly world of tanks undisturbed while complaining he can't help anyone right now because he's super busy.
It's not universal behavior of course, and I'm not advocating for RTO or workplace surveillance, but exclusively 'on-line' presence does tend to bring out the worse in some people, especially out of those who are not contempt with their job they chose and will do anything, other than quit, to not do their duties and hold others back.