Yeah kind of scummy to get them fired elsewhere too. CEOs and board members do this all the time but god forbid middle class try to get ahead by working hard.
The difference is in hiding the fact and being transparent/disclosing it. Are you seriously saying you think it's fine to not disclose one or more other full time jobs you're doing at the same time while working remotely as developer?
When you complete your work - that's a big if - your company probably won't give a crap about the rest and will want to keep you.
If you keep barely completing fraction of your work, say 5% what you'd normally expect, it's a problem and looking at contract agreement where you agreed to work certain amount of hours for exchange of salary - that is not full-filled starts to matter.
Same way from PoV of employee it would not be fair if company would start to wire you fraction of agreed salary because they're also working with other developers at the same time and you just have to deal with it.