It's unlikely those customers would then recommend the original builder on here, right? Out of interest, is it the customer that noticed the work needed re-doing in those sorts of examples?
Unless an independent 3rd party with the relevant knowledge checks and signs off work as it progresses...
That's a very simplistic viewpoint.
Also important to a customer:
Price
Accurate timeframes
Communication
Reliability
Leaving site tidy etc
No fuss rectifying snagging
Anything majorly sh|t doesn't take a tradie to spot it anyway, so a good customer recommendation should at least rule out cowboys.