I don't know if they're collecting for a class-action, but they might be.
It sounds like they think WotC has been, at best, sloppy with their royalty accounting and at worst purposefully underreporting.
When an author sells a work (to a "paying" publisher recognized by SFWA) they sign a contract stating what percentage of royalties they get, and then they're given an advance based on projected sales, etc etc. That advance comes out of the future royalties.
So, say, you're getting 10% royalties on a 20$ book. Every book that sells, you're supposed to get 2$ of it. Say, then, you get a 2,000$ advance ... until the book sells 1,000 copies, you don't get a check for royalties.
Until your book has sold enough copies to meet your advance, it hasn't "earned out". Apparently, most books produced don't "earn out", really, unless they go above mid market, but it doesn't reflect too badly on the author (I.E. they don't earn out to the tune of 20-200$, as opposed to thousands). Just that the author is never going to see a "royalty check" from that book before it goes Out Of Print. They got all their royalties up front (and earned a slightly higher percentage, at that).
Of course, most publishers also have a "hold against returns". For instance, say a Large American Bookseller "buys" 1,000 copies of your book. They haven't bought anything ... they're just putting it on floorspace in their stores and at any time they can return the unsold portion to the publisher without paying them. A sale is when a person picks up the book, walks to the counter, and pays for it. The hold against returns is the publisher's hedged bet that, between one accounting period and the next, (X) many people who bought the book may decide they didn't like it and return it to the bookseller, who will return it to the publisher. This can cause royalty checks to be artificially deflated ... your book may earn out within half a year, but the hold-against-returns may mean your royalty checks are 0.00$ until the publisher's hold passes ... where-upon you'll see a lump sum for all the sales that occured under the hold.
So it seems like their complaint is that WotC has a widespread practice of under-reporting or hiding sales to keep books from earning out or using an estimation practice that's not approved (apparently nobody uses real numbers anymore, most accounting is pretty much future projections). They may also have an iffy holds practice, but I'm not aware if that is approved by any governing body.
--fje
