Does “readily available” equate to “on your person at all times?” I’m sure the greats all did so before flash drives of sufficient capacity were available, right?

Should a professional accountant keep copies of all the tax returns they prepared, on a flash drive that’s with them at all times, in case a client gets audited? Should I keep a copy of every line of code I ever wrote? Where does this professional responsibility end for you?

I've written and published myself. Keeping manuscripts handy is part of the job. The problems mentioned in the twitter thread didn't exist before digital distribution, so what authors did beforehand is a bit of a non-sequitur. There were fewer of them, and the ones that made a living by it had real support on the business side of things, something vanishingly rare nowadays.

Accountants are required by law to maintain a minimum of seven years' worth of records for exactly that reason.

Fundamentally, if you want to sell a book you've written, no one is going to care more than you. That means that if you're a small, unsupported author (the vast majority of cases), it's on you to take care of the annoyances that come along for the ride. That's the nature of work. That flagging can be used as a form or harassment is a genuine problem- this is an inevitable side-effect of systems designed for pure automation, without a human in the loop to provide feedback. Over-reliance on automation is an issue that goes far beyond the world of publishing. That is orthogonal to the issue of being responsible for one's own creation, in terms of having needed resources on-hand.

Would you have your portfolio on your person at all times? Probably not, but you wouldn't go on a long trip without it. If you were actively working you'd have it available. If you didn't have it, you'd accept the risk of losing a contract or having your work temporarily withdrawn from sale. Maybe a bookseller would notice typos in your current edition and takes your book off the shelves until you can make a revised edition.

I mean, fundamentally, if you're saying your book needs to be on sale 24/7/365 then you need to be standing behind it 24/7/365 or paying a person or organisation to do that for you. If you want to take a break from the business of your book you should be prepared for Amazon to do the same.