The general problem with this one is that there are a thousand legitimate reasons not to hire someone that are also infeasible to efficiently establish the veracity of.

Suppose you post a job because you'll need to fill that position if you get a contract you expect to get with 85% probability. You legitimately expect to hire someone but can't in good faith make anyone an offer until the contract with the customer is signed. Then the contract negotiations take longer than expected. You still expect to hire someone soon but the deadline keeps getting pushed back by the delays, and then you have to keep interviewing new people because the ones you interviewed last month took a position somewhere that gave them an offer sooner. You might not hire someone for a year, or if the negotiations fall through you might not hire anyone at all, but at no point were you acting in bad faith.

Suppose you actually need to fill a position as soon as possible but it's hard to find a qualified candidate. There are, however, countless unqualified ones who ignore the requirements and apply anyway.

What do you propose to do with that? It's obviously unreasonable to penalize a company for not hiring unqualified applicants, or for doing the right thing and not making an offer until they know they won't have to rescind it, but then anyone can list those as their reason for keeping their listing open for a long time. Whether it's true depends on the company's internal state, which the company can thereby fabricate however they want. It's easy to write a job posting with stringent qualifications that gives you cover to reject any applicants for any period of time, and effectively impossible to distinguish that from an employer who actually has stringent standards.

The actual way to improve it is to reform the laws that cause companies to list jobs they have no true intention of filling as a requirement for complying with some other law.