(This is not a value judgement of Mastodon vs Twitter)
If this incident truly represents Twitter's change in approach to third-party clients, that change in policy is being executed in the most petty and malicious way it could be done.
This is not to excuse Twitter's actual behavior, which is clearly shitty. But: More petty and malicious would be to shut off access, then contact devs and promise that access would be restored if they just make these tiny changes to their app, and also sign this NDA forbidding discussion of the process. Then string along for a week or a month demanding just one more tiny change after change.
Then ghost.
Oh, you had a plan, but you couldn't really get it up in time, well, that's some learning pain. I'll cry a tear in some beer with you.
Tried to make a plan, realized there was no alternatives, but carried on anyways? That's very brave (ahem, read not smart) of you, but if you're a sole proprietor with no employees depending on you, then we can also share a beer of how to be smarter in the next venture. Got employees that are now hat in hand because of your "bravery"? Nope, again, no sympathy for you, but I'll be at the bar with your laid off employees burning you in effigy.