Let's say I'm a competitor, and I find that Niel (randomly picked) is someone I want to hire. All else being equal, I offer him $100k (website says he's making $88k). He comes to his boss to say "I like it here, can you match it?" What does his boss do? Especially, if he's valuable to the company... What if I have a very specialized skill that doesn't fit nicely into your matrix? Let's say market pay for my skill is…
There are some significant advantages in building an open team like this. People know what's their pay-grade and what part of the company they actually represent. If they don't think their cut is fair they can signal it. Many companies have confidential salaries so even when you know you are underpaid you can't argue it without throwing peers under the bus for revealing their salary to you.