You problem definitely is not mixed use SSDs. The Compellent Storage link makes that distinction, the PS Series does not. Drives go through a qualification process and multiple vendors are sourced for each drive type and size.
That part number also shows for a Compellent array so I'm not sure if that will work in an EQL array.
But it is that special process when the drive is made that is detected by the EQL array firmware.
I received the following response from a Dell Enterprise Infrastructure Specialist:
"Unfortunately, these HDD are End Of Life and we already run out of Refurbished stock as well."
They couldn't give me any more info than that.
An option is getting it back under contract. Standard contracts are for up to 7 years from original ship date. The 6210 isn't that old. Past that there is now an extended hardware only contract to take that to 12 years total.
Otherwise you are looking at other 3rd party maintainers for these drives.