In short, we can’t give you a simple number of as a request rate because the limits aren’t based on your assumption of tenant, user, and/or app-user.
The new documentation is our attempt to document a previously opaque topic, not a change in the technology. That said, our site reliability engineers do sometimes apply additional limits if they detect something they consider to be API abuse. This can mean an app that was making, for example, 20 API requests per second, is suddenly capped to, for example, 2 API requests per second. These additional limits are applied per tenant. The best way to resolve such a case is to first implement the rate limiting precautions listed in the rate limit documentation, then work with your customer through Atlassian support to remove the abuse flag.