I am using both esxi 6.5 U1 and esxi 6.0U3. On the latter, there is a 2-3 min delay by sfcb to process request to provider from the (windows 2012 server) guestOS to get data from host.
In esxi 6.5U1 the delay is few microseconds.
I checked the same using vmware workbench WBEM queries. The same is seen there as well.