Dave - smart questions, some details for you -
Each key is instrumented with both a finger sensor pad array, and butterfly mechanism sensors. (All wear-free, capacitive sensors).
The key down sensor reports the physical state of the key, regardless of location or even presence of a finger (it can detect the key down even if operated by a chopstick).
One key down event produces one entry.
Because all sensors are independent, we can read all of them in a single capture frame, effectively concurrently. One does not block any other, so n-key rollover is straightforward. We can assign the input patterns to mean anything we want in software.
That means that we could indeed assign two fingers down to mean two strikes on different pads, even on the same physical key, and even with the same keydown butterfly sensor event.
Having said that, here's what we observed -
Our development revealed much about the human perception aspects of a typing instrument. This particular area gets to the essence of why the hybrid of multitouch with precision travel is so powerful. People need that satisfying thunk of affirmation that you got the key. Especially at speed. It turns out that it's really jarring to occasionally get no feedback, when every other strike has such a robust positive feel.
So the way we configured our pattern assignments is for one strike per character, which feels awesome. It's possible to reconfigure this with software updates, but we think the current system works much better than those alternatives.
A more common example of the case you mused about, is with the shift key. Let's say you want to make a capital A. On TextBlade you have two ways to do this - shift with right pinky and strike A with left pinky, or tap shift with left pinky then strike A with the same pinky. The latter works out to be popular and quick.
On a legacy keyboard, it turns out that cheating by moving your ring finger away from home, and then doing the coordinated acrobatic timing for the concurrent shift with both fingers is slower for most folks than a sequential tap. People do it, but it's more work.
Super fast typists often hijack the caps lock key to improvise a tap mode, and turn it on and off with the same pinky just to avoid the deviation from home for the ring finger, and that concurrent two finger stretch. TextBlade has smart tap built in so you don't have to manually extinguish caps, saving more time.
What we've found using TextBlade is that the dedicated smart key for every finger tends to naturally encourage you to avoid the cheats with the wrong fingers, and you end up typing better.
Since TextBlade is a fully software-malleable typing instrument, all of this can be experimented with and evolved from popular usage. We expect more interesting learnings and opportunities will present as the user base grows.
Gotta go now, thanks for that insightful question.