At any time, one port group NIC array and a corresponding set of active uplinks exist. When you change the active uplinks, you also change the standby uplinks and the number of active uplinks.

The following example illustrates how active and standby uplinks are set.

1

The port group NIC array is [vmnic1, vmnic0, vmnic3, vmnic5, vmnic6, vmnic7] and active-uplinks is set to three uplinks - vmnic1, vmnic0, vmnic3. The other uplinks are standby uplinks.

2

You set the active uplinks to a new set [vmnic3, vmnic5].

3

The new uplinks override the old set. The NIC array changes to [vmnic3, vmnic5, vmnic6, vmnic7]. vmnic0 and vmnic1 are removed from the NIC array and max-active becomes 2.

If you want to keep vmnic0 and vmnic1 in the array, you can make those NICs standby uplinks in the command that changes the active uplinks. 

esxcli network vswitch standard portgroup policy failover set -p testPortgroup --active-uplinks vmnic3,vmnic5 --standby-uplinks vmnic1,vmnic0,vmnic6,vmnic7