Dress codes are a different manner.
Another point I didn't mention was they were very unhappy that the company and the contractor were in the exact same line of business, this is often an indicator of problems. A company that makes dispatching middleman software for the taxi industry couldn't possibly care less about what an end user of their software wears while at work. On the other hand, a company that's a stealth taxi driver employer is going to get all out of whack about employee dress codes, even if they call the employees "contractors".
"Do it exactly how we say" is classic employer relationship. "Produce this documented contractual end result" is more typical contractor relationship.
I'm not saying that wearing torn jeans and tee shirt to a financial contract job is wise, in practice dressing that way is probably a good way not to get renewed. Dress codes are for employees and if they're happy with the risk reward ratio for turning contractors into employees, well, that substantial and expensive legal risk is their problem. Maybe for "image" and marketing reasons it really is financially worth it for them.