I have had replies on bug bounty reports in under 10 before. It can and does happen.
Edit: To clarify, especially in cloud environments (which is most stuff these days) it's really not hard for someone to verify something if it's well written.
I might be a bit pessimistic here, but I'm betting that's not an experienced, trained individual that's responding to the ticket. It's like a level one techie who's basically just moving the ticket from one queue to another and potentially waking someone up if it looks scary enough.
It's certainly possible. I've handled a bunch of bug bounty programs and sometimes submissions come in at just the right time and attract just the right attention. It's not a reasonable expectation for the average submission.
It depends on your targets, IME. Huge companies? Yep, you'll get a "thanks for telling us" from a bigger bug bounty program and then not hear anything for weeks to months.
For small- and mid-sized companies that do bug bounties (of which there seem to be fewer and fewer these days as a percentage) you can definitely wind up submitting directly to the right people and get really quick response times.
Edit: To clarify, especially in cloud environments (which is most stuff these days) it's really not hard for someone to verify something if it's well written.