> I think the question is it a per-feed rate limit or an all-feeda rate limit.

It's an all-feeds rate limit. This is also implied by the quoted comment:

"It looks like only the first request in each batch works, then the others fail."

It also follows from common sense. Why would all of the people who are seeing this problem be refreshing their feeds more than once per minute? I'm not aware of anyone who does this, and feed readers don't support it. Mine is once per hour. But 25 feeds is 25 requests within a minute.

Ironically, just loading https://www.reddit.com in a web browser is around 150 URL requests.