Staging ESXi 6.5U1 to ESXi 6.7U1?

Hi,

Environment:

vCenter 6.7U1b

ESXi 6.5U1

I've uploaded Dell custom ESXi 6.7U1 ISO to the vCenter, created a baseline and attached the baseline to my Dell R430 ESXi hosts. I notice when the ESXi 6.7U1 baseline is selected, the "Stage" option is dimmed in both vSphere Client and vSphere Web Client. Is this expected?

I want to upgrade multiple ESXi hosts over WAN links and don't want to transfer the ISO files right before the upgrade. If the ISO can be uploaded to the ESXi hosts ahead of time and upgrade via command line, why can't upgrade be staged like patching?

Thanks,