"So you're saying theoretically I can leave the ATE fluid in longer?"
Longer or the same.
It's more a matter of personal preference because ATE meets or exceeds DOT 4 specifications.
BTW, many of the Stability Control Systems and anti lock break systems are made by Bosch and sold to BMW, Porsche, Audi, Skoda, VW, Citron, ect ect ect.
If Porsche uses ATE in their maintenance program here in Germany I am positive there are no issues with a BMW.
"I would think the dealer would not be foolish enough to put a fluid in or perform any work that could potentially invite liability, no?"
- The BMW dealer is ONLY authorized to use BMW approved fluids which ATE is not on the "approved" list. Neither is Redline or Amsoil for that matter. The BMW dealer politely handed me back the ATE super blue, but the Porsche dealer gave it back 3/4s empty.