Could be smoke but there are a lot of flips happening so it seems to be legitimate.

I have had them for six years when I started buying foreclosures and was inexperienced and naive wanting to fill vacancies right away to enable myself to buy more properties. 

There are some legitimate full service turnkey providers, and there are definitely a few sharks out there as well.

All of those expenses are valid and legitimate, and must be covered by your rental income if you bought right.

The guys I chat with about "daily investor things" know who the original contractor is, but I don't know if I'm enabling unethical contractor behaviors by not leaving written reviews. 

Even Madoff had a legitimate company his sons ran on the 19th floor. 

Am I required to keep such info confidential, or is it legitimate to give to their new landlord?

If they know they can come to you with legitimate complaints about bad guests and you actually do something about it, then hopefully you'll be on good terms once everyone gets used to the situation. 

And I’m legitimately asking because I always either never get a response or get a “call the office/ call this number.”  

I do this so often that I created an online tool which enables me to instantly estimate a break-even price (where rent equals recurring expenses).