While it's hard to reasonably argue that employees shouldn't know the valuation of their own equity, it's easier to argue that the cap table isn't any of their business. More information is usually better, but I might not push too hard on the terms of everyone else's shares.

Liquidation preference is an important one to know, and it's easy to make a case for it: when you're discussing valuation during negotiation (and you need to), and you get to the part about what the numbers look like if you're bought when doing $xMM/yr, you get to ask "how much of that number will VC take off the table?"