For me, it sounds like it is. I would like to know your opinion though. In this sentence: "I have to get back to work.", 'get back' means to return. If I understand correctly when we pronounce phrasal verbs in a sentence we usually stress the particle a bit more than the verb. Am I right?
Yes, this is a phrasal verb and the particle is always stressed.
We use get instead of go in situations where we're losing time, or running late, or when someone is wasting time at work, school, etc.
It's already 9:15 - I need to get to work.
Stop looking at your phone and get back to work!