It isn't true that every test used tiering. In fact, the choices weren't tiered in the video that is running around that shows how the kiosks work.But people didn't just pull that out of the sky. That's how it has been tested for YEARS. Before acutal FP+ testing, they tested it out with the birthday promotion and the "give a day" promotion.
I actually believe the tiering is a critical piece of making this work. It's their way of rationing rides. Since it's all wrapped up in a magical band, people will swallow it in huge numbers without complaint. If they had merely rolled out a limitation of Fps distributed (only 2 headliners per day or 1 per ride) on the current system, the outcry would be even greater. The rationing will free up more "FP currency" to bestow upon people through "suprprise and delight" opportunities, or perhaps as enticement to stay onsite.
I'd LOVE to see the new system roll out with no tiering. But I'd be shocked as heck too.
It should also be noted that if hey only allowed one e-ticket attraction in the three preselects, then there would be a huge number of e-ticket slots left available; many more than would be needed for pushed offers. I'll not bother discussing the on-site issue since that concept runs somewhat counter to their public statements.

I know! I've heard so many reports of standby lines already being much longer than what has been listed as the wait line.
We only ever get FP's for the Mountains at MK and Peter Pan, EE and Dinosaur for AK, ToT, TSMM and RnRC at HS, Test Track and Soarin at EP. If I can't get more than one, why would I use it?