https://www.abuseipdb.com/check-block/198.143.164.0/24
As reported in https://wordpress.org/support/topic/api-wordpress-org-is-on-abuseip-db-blacklis/ it looks like some hosts have been confusing outgoing connections to api.wordpress.org as being incoming brute-force requests, and reporting it as such.
It appears that some hosts/networks may be using this as part of a network DROP rules causing WordPress sites being unable to connect to the APIAPI An API or Application Programming Interface is a software intermediary that allows programs to interact with each other and share data in limited, clearly defined ways.. I believe this might be the cause of some past issues where .251 was inaccessible but .252 was.
Can someone from systems request removal, specifically for https://www.abuseipdb.com/check/198.143.164.251