OK, I solved my own problem with the stuck Pbrake pedal. First of all, there is no connection between the service brake and the Pbrake. Either mechanical or electrical. I guess the wording in the owners manual that says to apply the service brake then release the Pbrake is there just to keep the vehicle from rolling away.
The issue with the stuck Pbrake pedal is real. And it could happen to others. Here is what I found. The Pbrake pedal lever arm is formed with a cross section like an upside down U shape. One side of the upside down U is the actual Pbrake lever arm. The other side doesn't look like it does anything. Maybe just for strength? When I depressed my Pbrake, that open side of the upside down U slipped past the upper edge of the plastic kick panel that is next door. Later, when I released the brake, that open side of the upside down U caught on the upper edge of the plastic kick panel and would not allow the Pbrake lever arm to return. To prevent this from happening again, I cut away a sliver of the plastic kick panel upper edge. Now the Pbrake lever arm can not catch.
It would not have mattered what kind of release mechanism the Pbrake used (gear shift selector, dash mounted lever, electric automatic). Lexus deserves a kick in the pants for this design. But I guess they are too busy pursuing perfection to notice this fault.
