Does Alert history still work with prometheus?

[wuarthur]

I found some conflicting information

#5083 says all alerts is pulled from alert manager.

But in #3684 it says the alert history is from Prometheus as described in the readme

[prymitive]

Which bit is unclear in the readme?
The list of currently firing alerts comes from alertmanager.
Prometheus provides information on how often each of those alerts found in alertmanager fired in the last 24h.