The article explains why we are seeing a delay in receiving EVPN core isolation when the physical interfaces are going down.

We can expect this behaviour when BFD configures.

When BFD is configured on the switch, an uplink failure does not immediately bring down BFD, BGP, or EVPN core isolation. The sessions remain operational until the configured BFD detection timer expires. Once the timer expires, the routing protocol sessions (such as BGP or OSPF) transition down first, followed subsequently by EVPN core isolation.