Who knows about "rubb-in" tests?

I have been reading some time ago that something called the « rubb-in » tests has been moved from Japan to Taïwan.

I suppose that these tests are made by the burner manufacters on samples send by the blank media manufacturers in order to adjust the writing strategy for a given media and so improve the firmwares
Is this right or not ?
I have been searching around in forums for more detailed info about these tests, but could not find anything …
So I like to know if somebody knows something precise about where and how these « rubb-in » tests tests are done.

My aim is to find out precisely which samples of a given MID code have been sent for these tests
For example Verbatim is manufacturing the same MID code at least in Singapore, Taiwan and India and I like to know which ones where used for adjusting the firmwares.
I think this could explain why we have all these differences in burning quality among a single MID code

A other question: these tests are first made when a new MID code come out. Who can garantee an absolutly constant quality of manufacturing during the whole lifetime of a MID code ?