I don't think, I'm in the same situation. Even though is not "legal", it is well known that people under LMIA or in general temporary workers encounter a lot of manager that are really unpleasant and do bad things only because they know that you are in this status. I can say this from my experience and that's also my agent's experience. Anyway immigration, I suppose, wants only to know if you really have that work experience, they don't want extra work to verify why your manager has a negative feedback.