
I think that's irresponsible advice.
First of all, a lot of company owners outsource web copy to software people, try to write it themselves to save money, etc. That way, it comes out pretty terrible, but that doesn't mean that they are operating any kind of scam.
Secondly, offering "top notch" work is the same as offering "top notch" anything-- marketing.
A better indication of a scam is to look out for companies that promise "guaranteed A/1:1" work, which is illegal. Even that's not foolproof, though.
The only foolproof test is to order a small sample before committing to a company or writer for more than, say, 2 pages.
If those 2 pages work out, request or otherwise go through that same company and/or writer to complete the assignment.