It makes sense from certain perspectives. I think when you are a Nutanix and trying to break into HPEs customer base, it's a lot easier to break in on a standing vendor-of-record agreement than it is to try and break in some other way. HPE sees an opportunity to bring in a much larger and more complete HCI offering than their own which DOESN't translate to more licensing revenue for the DellEMC machine through VMware.
My biggest problem is I have customers running Nutanix on Lenovo and Dell hardware now and the support is kinda crap compared to my customers running on Nutanix-branded appliances. First and second level go through OEM before it goes to Nutanix, and they're the experts at fixing their own stuff.
I would think Simplivity customers should be on notice though, if this partnership results in significant market gains for HPE I think that will be the end of that experiment.