[actualprogram]

Let's review the conditions of your example:

  no source,
  no debugger,
  two function calls

And the assertion that // works as a strategy. There's only two things you could possibly comment out, so really the example is not so much "explained poorly" as "conceived poorly". Don't shoot the messenger - it's your example.

As for the further explanation here, allowing a debugger makes the search irrelevant - there's only one piece of information the binary search can tell you: which function causes the segfault, but as you observe, that information's available from the debugger already. And no, it doesn't matter if you reframe things as "a percentage of an instruction stream".

The objection to binary search is not "binary search in the codebase can never tell you anything," it's that it's a method that can't -- not "doesn't" but "can't" -- produce a non-trivial testable hypothesis. Does this mean you can't ever use it? You may have no choice. But it's a terrible place to start, and most of the information it offers is available through other means, often with more precision.