Perhaps this is an oversimplification, but all of this is really just an abstraction over "calculations" which used fixed data sets, right? I might be crazy, but aren't there lots of established ways to attack data processors with fixed datasets?

Example: algorithm (A) processes dataset (D) to create output (O). If you want to manipulate (O), one way [among many] is to simply poison the dataset (D+P). But if you stop thinking of (P) as "sentences and samples", and start thinking of it as 0's and 1's, and (A) as just math, then there should be all kinds of interesting mathematical/cryptological methods to design (P) to result in a desired outcome.

In other words, it's just math. Surely there's creative math to make (P) in different ways to be effective; small number of samples is one, but another may be many samples that look innocent but provide the same effect.