Interesting points on both sides of this issue.

I believe all parties agree that with a lack of actual technical data around the transmission operation, wear, fluid degradation, etc., then empirical data becomes a major source of information. But even here, when speaking specifically about BMW transmissions, we have a lack of actual data. Sure, there are folks with actual experience with transmission failure or friends who experienced it (so one, two, maybe five data points), but what of the million plus units that BMW and their suppliers have put out to date?

Is there consideration to any "motives" that BMW might have in recommending extended servicing of the transmission:

1. BMW wants your transmission to fail as soon as possible so you will buy a new car sooner?

2. BMW doesn't want the income (or more accurately the dealer's income) that would be generated by servicing the transmission every 5,000 miles, 10,000 miles, or whatever mileage number you'd like to insert

3. BMW believes their engineering staff in that the transmission doesn't need regular servicing of the fluid (again, the term regular seems up for debate). Perhaps the engineers are using a balance of technical and actual field data. Maybe the engineers were tired that day and just guessed?

I think this list could go on and on, but I find it hard to believe that BMW choose the recommended service interval for no particular reason (good or bad).

If 5 out of 10 BMWs were experiencing transmission failure at 50,000, 60,000 or even 100,000 miles, you would think the word would be more widespread.
I'll be the first to admit, I haven't been following BMW drivetrain reliability over the past years, but by the looks of some of the BMW owners on this forum and the number of posts (length of membership), there should be some word of transmission failure problems if it is occurring. Perhaps the majority of members are not keeping their cars much past 100,000 miles, but I think some history would still show up.