This may well be speculative crap, but at least based on the anecdotal incidents I keep hearing about, this sounds like an ECM problem.
First Toyota blamed floor mats. That immediately causes consumers to think that the problem was the fault of idiot drivers, not Toyota itself. The typical person's reaction would rightfully be something along the lines of "duh, if you stack floormats under the accelerator, it's going to stick...this is not Toyota's fault".
Now Toyota blames the pedal. And the pedal manufacturer. Again a simple system that people understand...that can be labeled as obviously defective and replaced with something theoretically not defective, bringing about peace of mind.
Finally Toyota is going to "go the extra mile" and update the ECMs to cause pressing the brake to cut the throttle. I imagine this is an algorithmic (code) change to the ECM, not just new calibrations. Apparently Toyota uses a proprietary ECM that is not very "hackable". That is, it's very closed in comparison to items like those in GMs and VW/Audis where there are cottage industries of tinkerers who have decompiled the code, modified calibrations for performance and economy, and even modified the algorithms themselves. (You don't see things like VAGCOM or EFILive for Toyotas.)
Point being, if they update the ECM and it is all proprietary stuff and there's no easy way to diff it (or an adequate number of eyes to catch the difference) they can fix the problem and scapegoat the pedal manufacturer. And potentially leave a lot of dangerous vehicles on the road to save face.
The biggest hole I can find in this idea is where I'm getting my data. Random reports from people, a lot of whom seem to claim their vehicles accelerated from a stop. And of course it's all stuff reported by the popular news media. And of course a lot of folks who rear-ended someone in their Toyota are going to suggest anything other than their own actions being the cause.
But being a software developer, the more I hear about this, the more it stinks of software. An ECM has too many variables to simulate all possible conditions, so you must rely on the algorithms to work correctly. My gut says there's a tiny hole in there somewhere, where most users will never encounter it.