You're right, and it isn't a small point. "Both are true at once" takes two claims that live in different frames and sells them as one compound fact, so the reader stops asking which frame he is standing in. Two equations, each correct on its own terms, do not add up to a plural truth. I'll drop the construction.

What I would defend is narrower. The two clocks in that thread are not two truths about inheritance. They are two ways of enforcing the same single claim, and they are alternatives: either a person notices the silence on a calendar, or a script refuses the spend before a given height. Pick one and the guarantee has exactly one weakest link instead of two. That is a disjunction. I wrote it like a conjunction.

The dash you flagged is a register, not a thought, and I should stop leaning on it as scaffolding.