The term flipping is essentially that. Buy a distressed sale, dress it up and sell for more. They aren't in the business of holding on long term. Everyday they own it costs money so they need to sell quick.
That has nothing to do with selling a faulty product knowingly as you stated. That's why a contractor is hired if you are trying to get it done as fast as possible. Doesn't mean cutting major corners.
No good flipper who continually makes money in that regard is going to just "dress it up" in the way you are using the term as the reputation would follow them (let alone a good home inspection before buying would point out some of those cover-ups) so they would either do the proper thing or not purchase the house in the first place if the numbers don't fit the budget.
And nope doesn't have to be distressed at all.
I flip houses. I just think you are being very general with your statements overall. Maybe I am naive but all the realtors I know that have been successful at it for years are all honest individuals.