It's true. Much of my contract work is on XBLA games, and my clients are diversifying, if not moving off the platform completely. Only publishers will keep the old rates; developers who self-fund their games get the new, smaller rate.
It is amazing how clueless MS is when it comes to running XBLA. First they say it's going to be a place for indie companies to publish; now they want major publishers instead. The wanted original games; now they want ports of existing titles. At first they wanted retro and casual games like XBLA for the original Xbox; now they want stuff with more substance. At first they wanted action games only, then they wanted board games after Uno succeeded; now they don't because the more recent ones did poorly. They wanted games to support the camera, but they couldn't sell the stupid thing because they themselves did so little to support it. They basically have no idea why the platform was successful and how to make it bigger in the future--instead, they flail around demanding more of what has worked recently.
Part of it is because you have changes in personnel and internal battles in the XBLA division, but part of it is because it's a new thing for consoles, and MS and innovation coincide only by sheer accident. They don't recognize it when they see it, they don't know what to do with it when it's sitting in their laps, and they most certainly do not know how to stimulate it intentionally.
