This is correct behavior and is because of the Wi-Fi Private Address feature of iOS/iPadOS/WatchOS.
In fact, the entire ability to be able to discern the vendor for a particular device by doing a vendor lookup on its MAC address is one that should not be counted on to work in the future.
Assuming "EE:9C:BC" are the first six octets of the MAC address, that is a valid local MAC address as specified by RFC 7042, which specifies bit 2 of the initial octet of the MAC address as the "local" bit.
This means for unicast addresses:
x2‑xx‑xx‑xx‑xx‑xx
x6‑xx‑xx‑xx‑xx‑xx
xA‑xx‑xx‑xx‑xx‑xx
xE‑xx‑xx‑xx‑xx‑xx
are all valid local MAC address ranges; for multicast, it's:
x3‑xx‑xx‑xx‑xx‑xx
x7‑xx‑xx‑xx‑xx‑xx
xB‑xx‑xx‑xx‑xx‑xx
xF‑xx‑xx‑xx‑xx‑xx
Therefore the router is doing the right thing in noting any device with a MAC address with bit 2 of the first octet set is "anonymous," as there is no way to work back from that address to what the actual device hardware address might be (which is the entire point of the Wi-Fi Private Address feature.)
I'm not sure why the router is identifying the 2.4 GHz vendor as "Apple, Inc.” though; does your router have multiple SSIDs and do you have Settings -> Wi-Fi -> (SSID) -> Private Address shut off for the 2.4 GHz network?
Regardless, what you see for the 5 GHz network is exactly what you should expect to see if Wi-Fi Private Address is enabled, and it appears your iPhone and router are operating properly.