I will be very honest with you, I am not aware of cases like that. I hope that it's an isolated case, but I will be happy to follow up on it.
According to our process, each time that an application is approved, we communicate with the applicant to inform them about the situation. At the beginning of the pandemic, we began to allow virtual admissions. We do communicate with people whose permanent resident applications have been approved. Though there is no interview in person, we communicate with them in order to admit them virtually.
I am surprised at the situation you are describing, but I will be happy to follow up on it.