One reason for disallowing the re-use of the same IP + VLAN for the management interface that is also used on an SVI is in the context of switch stacking or warm spare (VRRP) configurations. In those cases, the SVIs don't use the MAC address of the base switch. They use a virtual MAC for HA operation so that both VRRP members or all stack members are using the same MAC for client routing. However, the management interface always uses the MAC of the base switch -- as it always uniquely identifies the specific switch and is used for upstream connectivity to the Dashboard backend. Since it uses the base switch MAC, if you had an SVI with the same IP as the management interface, there would be an IP conflict in the network as both the management interface and an SVI would claim the same IP, but have a different MAC address for L2 addressing /ARP.
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