Why AP’s use multiple IP addresses

A Mist AP will pull a management IP address from the Native VLAN.

By default, a Mist AP requests only one IP address i.e. from the Management VLAN (VLAN 1)

Features that would require multiple DHCP addresses:

Local Status Page

As documented in AP Settings

If the Local Status Page is configured for the Site – all the site AP’s will pull their own IP address from the Management VLAN, but also addresses for each of the VLANs configured on the AP.  This is at the site level so this needs to be taken into account when doing DHCP planning.