And it is correct to call Primal a platform rather than a Nostr client since the feed is centralised and it could potentially suffer from the same issues as other centralised platforms.
Discussion
How is their feed centralized if they literally allow you to add relays AND switch caching servers?
Unless something has changed recently, it only uses the relays that you configure for writes. Reads are exclusively from the cache and therefore the cache can be manipulated in any way they want to. I verified this by blocking access to the cache IP with a firewall rule and the feed stops working.
I agree that switching cache servers is an option but at this point I’m not aware of any alternative independently run cache servers.