Couldn't it work just as easily the other way? Especially with tech in such high demand.
Posting wages might make it easier for companies to offer higher than others in an attempt to attract talent, leading to competition in the market, and salary inflation.
Sure, it could; I was just describing one way that posted wages could lead to stagnation.
I suspect that different things will happen in different markets. It seems (to me) that software development may be unaffected, administrative workers might benefit, and unskilled workers may suffer.
Considering I hear every company boasting of "competitive wages" which hasn't lead to any sort of massive wage race, I would expect they must have some understanding already. If anything this just removes the information asymmetry between employer and employee.
Posting wages might make it easier for companies to match their offers to others, leading to a sort of collusion, and salary stagnation.