There is a world of difference between Advance Reader Copies as Baen does them and so-called Windowing. According to Baen's site:
An eARC is an electronic Advance Reader Copy. This is an unproofed manuscript and is guaranteed to be full of typos and error. It is pretty much raw from the authors word processor. But you get the entire eARC well in advance of even the Monthly Baen Bundle release.
Contrast this with a finished book which is withheld from most of the market for a year or more in an attempt to attract a premium price for the hardback edition. Baen are offering an opportunity to pay a premium for a privilege not otherwise available. I have never heard a suggestion that Baen withholds releases to sell more earcs.