That they are a for-profit company is completely irrelevant, as is whether or not they have a bug bounty program. Legal abstractions aside, it's still just people on both sides.
The expectation isn't that the poster work for free. The poster could have easily obscured identifying details and the content of his article would not be diminished. It is my opinion that if he wanted to "show his work", work done of his own initiative, then I think it would be more interesting and useful to include something about attempting to assist in remediation. I think, as mentioned by others, it would make a far stronger argument to click that "hire me!" button than anything in his technical analysis.
Of course automated systems are on the hunt for this stuff. Same with public code repositories, Docker images, and if you operate a subscription-based service with any popularity then your web interfaces for sign-up, login, etc will be subject to well-orchestrated brute force attacks. That someone did a poor job is all the more reason to avoid potentially contributing to their exploitation.
A response within the positive spectrum is absolutely above and beyond. Of all the feedback this community can provide, I think this is the most useful and I'm grateful that the poster has been responsive to it.
I've made money from selling exploits to companies. Ive also been cheated out and had bugs downrated so they could pay less. Ive also seen colleagues who reported bugs they inadvertently found get hit with a felony (found not guilty).
Frankly, this company should thank its lucky stars that the disclosure was an 0Day and not "sell this on dark web and have it exploited for 3mo from 1500 accounts and drain the company's coffers".
This person owes the company *nothing*. They found an exploit due to bad API implementation, and wrote about it publicly. If they were in the USA, that's completely in 1fa territory.
It’s a for-profit company without a bug bounty program, in no way whatsoever should they expect someone to work for free to fix issues they created.
The keys are public, they made them public. Do you expect that there are not automated systems trawling apps from the g-play store and doing what he’s doing?