Hi tianhailong666,
Looking interoperability matrix for the vCentre 6.0U3 and ESXi 5.0, it confirms that this is not supported (link).
As you state, vCenter 6.0.0 supports ESXi 5.0 (link). I'm guessing that whilst Update 3 is built on the major version of ESXi 6; that VMware have a policy of supporting a certain number of historic versions (I.e. only supporting current version + 2 prior releases).
A glance here shows that there is no upgrade path from v5.0 and the same is true for ESXi (link).
The full Interoperability Matricies is listed here.
Not sure if this helps, as I understood your question up to the screenshots, which seem to confirm your comment that the vCenter 6.0 can support ESXi 5.0....
Diskonekted