I believe it's that they don't want to sell their cost-effective products without a large-volume (1E9 units/week) commitment. The folks on that side of the ocean have a peculiar way of doing business. They protect their IP by not telling you anything, but steal your IP the first chance they get, as it's "OK" to them.

If they told you how their stuff is supposed to be used, you could figure it out for yourself and make your own.

There is, after all, nothing on this device pair that would process the data format into something it could either accept or reject, aside, perhaps from bandwidth limitations, so it has to be leaving those details for the user to process. Nowever, the O/P hasn't shed any light on what he's done to come to the conclusion that he's getting garbage at times. If he's used a storage 'scope and captured the erroneous data, he's probably right, but if he's relying on what he thinks he's getting from the MCU, it's not so likely.

RE