Re: As I read it
HPE put their own firmware on drives - this makes sure that the status code can only be read by the HPS server. Therefore you can put the identical drive into the caddy and into the machine but it will tell you it's broken and will keep showing the status as degraded in the error logs and viewers.
At least with the older Gens (8/9?) that I tried putting SSDs that were better, cost 1/3 price than the HPE ones but weren't HPE certified.