No genetic bottleneck proves no global flood

Of course you can.Words can have different meanings in different contexts. Take "proof". In mathematics, it refers to a demonstration, absolutely and without any other possibility, that a mathematical proposition is correct - it's an on/off switch - something is absolute or not - there are no nuances.In criminal law, (in my country at least), it means proof beyond reasonable doubt. And in civil law, it means proof on the balance of probabilities. So it's very nuanced in law.Different contexts, different meanings.So if you change context, and the common usage of a word in that context is different from the usage in a previous context, you need to change your meaning. Tan isn't deciding what words mean - as an expert in the field, Tan is telling you how the word is used in the relevant context. I grant you, it's a slight pain, but it's the way it is.