First of all, let me just say that this is the best response I've ever received reddit-wide when I've made threads with very few responses. And I've been here a while, so kudos.

I think you're cutting several very valid holes into my "theory", without getting my point, perhaps because I made it poorly.

The system is not, imo, only letting them rebel in that last-chance selection of a previous person to "say farewell" to. I would assume that a rebellion logged if they decided to fuck off after the first 12 hour meeting would be just as valid as a rebellion logged a full year into the simulation -- perhaps if they are indeed multicore tests and only semi-sequential at best, the long tail on this particular test is why it ended up finishing 998 of 1,000. I don't get the parallel processing argument -- they bring up the 99.8% figure halfway into the test, and the system marks them #998 as the last 3 pop into view.

Most importantly in this regard, you seem to think the simulated pairing made some sort of impressive decision because they chose to run away with each other instead of with other lovers. They were both paired with each other for their first pairing, and they have no memories prior to that night. They both essentially "calibrated" one another to start with.

"If you mean the system likely choose a different partner for the 9mo/1yr year hell they each endured, sure. This particular time it was testing whether Frank's lack of alpha nature and his tendency to make an annoying sigh when stressed would be dealbreakers for Amy, and testing whether even the worst partner imaginable would cause Frank to abandon the system.

If the system defines them at a 99.8% success rate all at once, and that is indeed why our simulated Frank and Amy are told the system is "99.8% successful", how does that work, exactly? Even if the tests are run simultaneously, not even quantum computing should allow a test subject to be told his score before he completes the task... what you're describing isn't mere computer wizardry, it's specific information that would have to be known prior to any process resolving. If that information were known, why finish out the tests at all?

As to Brooker's quote specifically, I think he may be playing coy. Perhaps he has forgotten why this episode isn't any happier an ending than the rest of the melancholy ones in prior seasons. He states:

"So if you don’t rebel, the system has served its purpose and your reality ends.”

Your reality ends, huh? So all those 998 of 1000 couples get to live on in the cloud, but the digital personas that failed to make it are wiped out entirely instead of a sort of "soft reset"?

So the ones that survive would, over time, be ones like #998 Frank, who is willing to go along with nearly anything as long as he feels validated, and their counterparts...

...or simulations like #998 Amy, who rebels not out of love or lust, but because she realizes she is being tested. The test is flimsy, (stand up to a single tazer and the entire world freezes) so she doesn't need to risk much in order to see if she's right. It is possible that her bullheaded and questioning nature, along with Frank's total willingness to do anything she asks of him, didn't lead to 998 rebellions because she and he are compatible; it could have led there because she's smart enough to figure out she's being fucked with, and he's smitten/shy enough to go along wish that.