Early last year, the new Apple Mac Pro 6,1 (aka black can design) was certified and fully supported on vSphere 6.0 which I had blogged about here. Several months later, customers discovered that some of the newer Mac Pro 6,1 units were shipping with different model of their PCIe SSD device than what was originally released at GA. This was problematic because ESXi was not aware of this newer device and could not detect during or after installation. Although a work around was identified for customers looking to install either ESXi 5.x or 6.x on the newer Apple Mac Pros, it definitely was not ideal.
It has taken a bit longer than expected, but the issue has now been resolved with the latest release of ESXi 6.0 Update 2. A similar fix will be available for customers running ESXi 5.5 in a future update. You can find the direct download for ESXi 6.0 Update 2 in link below which includes a pointer to the release notes in case you are interested in other fixes included in this release.