At work we sell servers by HPE.
We create Install-ISOs from the included install ISO.
At boot the Installer checks if the system is manufactured by the vendor.
If it is: It continues boot and offers you the installer options
If it is not: It will fail with a message that the manufacturer doesnt match.
On ESXi you need to pass the argument smbios.reflectHost = true (or something along those lines)
Dunno how HPE customized the install.wim
But you can probably get those for cheap on ebay and maybe compare the wims for differences.