I had the same exact reply. About the Model 3s, yes, that's right, I have a 2019 Model 3 which doesn't have the heat pump (and it is super quiet). But I have tried older Model Ys with a heat pump and they were super quiet. I also had the answer "we can't use customers' cars for this purpose". Well, at first I seconded that and asked to show a model Model Y they could have there as a loaner or for showcase, and that's what they did. And there were two, one of the employees. And they were both quet. Then, when they acknowledged that there was a difference, we tried to understand why my new Model Y had this problem, and they could pull out a customer's new Model Y to compare. And that one had our same noise problem. So... if they want to, they can do it. They just tend to dismiss and ignore the problem as much as they can. I am sorry, but that's how they do.
At this point, if they are in complete denial, I'd change the service center. Another option is to contact your local Tesla Owners Club and ask for help from them. They usually can help with this sort of things. They are able to deal directly with the service centers and Tesla headquarters