Everyone revealing where they're at exactly (cash + bonus + stock + extra perks/PTO/whatever), while potentially a little uncomfortable in the beginning, is better for everyone long-term. I used to be against it, if only because I was typically at the top of the pay band for my role so had little to "gain" from the practice, but I've come around the last couple years. There's really very little downside, even if you're a top performer.
1. People who are legitimately being taken advantage of can more quickly realize it and either work to correct it or leave.
2. Top earners should be able to justify their outsized compensation to others, including peers.
3. Some people just legitimately don't know you can negotiate things like non-discretionary bonuses, extra PTO, etc.
4. Maybe your company pays everyone below-market, not just you, and at least knowing this will make it easier to decide if it's worth the lower pay (for QOL/WLB or whatever) or if you want to leave.