IPv6 - EUI-64 best practice
The EUI-64 host address configuration method is not recommended by Cisco (or by any vendor in general) primarily for privacy reasons. EUI-64 generates a stable, globally unique IPv6 address based on the MAC address of the device. Although this is very convenient, this means that the IPv6 address of the device can be tracked as it moves across networks, which can potentially be a privacy concern.
On the other hand, a random interface identifier generates a random, temporary IPv6 address. This random address can change over time and across networks, making it harder to track the device. This is why random ID generation is often recommended for autoconfiguring the interface ID.
Using random interface identifiers can help prevent certain security risks. If an attacker knows the MAC address of a device (which they could if EUI-64 is used), they could potentially use it to target the device with attacks.