Why aren't wages rising in a tight labor market?

>>> If upward real wage rigidity exists

How many people have formal annual wage negotiations? It's rare in my experience. But imagine a law that required say two 30 minute wage and conditions negotiations one week apart every year? For every employee.

Pretty much every other input has an annual contract and a negotiation period - suppliers of everything do this.

And then imagine a private industry of agents (call them selves Trades Unions perhaps) that would block negotiate for people signed up.

(yeah why is that not a thing?)