I accept I'm probably out of date, and a dinosaur, but in my case, if there was ever any question of my being read as trans then I would tend to rapidly volunteer the answers, because while I certainly don't wish in any way to invalidate the identity of anyone who chooses to be non-op, I am absolutely ultra-longterm POST-op and I wouldnt ever want someone assuming I wasn't, anymore than presumably someone non-op would want anyone assuming they were operative. The two identities are equally valid and equally genuine - but they are subtly different.
So in many respects I have to say I tend to agree with the author. In any relevant situation I'd generally like people to know exactly what I am rather than assume anything. Heck I would even get pissed off if someone assumed I'd had the surgery any less than the full 31 years ago that it was... In otherwords if they start questioning not only do I want them to know the truth, but I also then want them to realise that it all happened for me so very long ago that it really isnt in the slightest bit relevant. Paradoxically when that penny sinks in most of them then apologise.