No, completely wrong. Deep markets are not more accurate.

People who are unfamiliar with how regulated gamblings works assume that the "market" is just lots of informed people rationally trading with each other. This is not how it works. Bookmakers post lines to a small group of syndicates up to a limit, they will often do this non-publicly, and this is how prices are set. They are not set by the "wisdom of crowds", they are set by people who have invested hundreds of millions of dollars in predicting the outcome because bookmakers have an economic need for accurate lines.

When lines open to the public, there is often no significant movement after opening prices set by syndicates. That is because the public has no idea what the actual price should be, they are just uninformed noise traders clicking buttons randomly...that is the product too, the purpose of the product is entertainment not economic efficiency.

It is true that some lines are set incorrectly but the public is not able to benefit from this, because they do not have the information. I would guess that 95% of money made from gambling has been made by under 50 people. And, perhaps counter-intuitively, most of the time these people trading does not have an impact on price because they deliberately trade in a way that does not impact price. Again, the purpose is the same: they trade to make money, not produce economic efficiency.

The people who think prediction markets are useful in any way are people who never traded any markets and couldn't predict if the sun is going to come up tomorrow. If gamblers are noise traders, these people are noise speakers. These markets are completely pointless, gambling is economically pointless outside of the pleasure that people get from entertainment.