They have not given any other information on where to draw the line.
> even give a hypothetical example to illustrate this
No they didn't. They gave an analogy about how murder is bad. Which is no more helpful than "the most extreme possible interpretation of what the neurosurgeon said would be bad". They haven't given any examples of experiments that are okay or not okay.
All they've said is that a super extreme early experiment is bad, and then acted like the neurosurgeon said they wanted to do that. They are either ignoring the possibility of less extreme examples, or acting like everything the FDA doesn't allow is exactly the same.
I can't tell you which it is, so if you insist it's not the latter then it must be the former. That's just as bad. It's a strawman.
If they gave a non-strawman non-FDA explanation of where to draw the line, then I must be blind, so please quote it.