all builders are cowboys

Maybe this is regional. "Cowboy" in reference to a tradie means someone who is untrustworthy and out to rip you off or cheap out on work. They'll do the work but often to a low standard or with major defects they try to hide.

Every house is different and so every job is custom. Whatever standards you think the builder is enacting to get the job done to an agreeable price is likely an ad-hoc solution that you yourself could have done as an amateur if you had the tools.

For every standard to be met, you compromise either on cash or time.

They don't really do rework they'll rather keep plowing on assuming some slack in an ethereal safety margin.