@MDowns 

What you are seeing is expected behaviour, not a bug in the Omada controller.
Disabling IPv6 in the controller only tells the Omada gateway (the router) not to hand out IPv6 prefixes or addresses on the LAN; it does not stop the gateway from receiving IPv6 traffic on its WAN port, and it does not stop the DNS proxy (dnsmasq) in the gateway from answering AAAA queries that clients send to it.
The DNS cache you are looking at is simply showing that:

• A client asked the gateway for the AAAA record of some host.
• The gateway forwarded the query upstream, got an IPv6 answer, cached it and returned it to the client.

That is all normal.
The fact that the client obtained an IPv6 DNS answer does not mean the client can actually use IPv6 to reach the destination; if the LAN interface has no IPv6 prefix, the client has no global IPv6 address and therefore cannot open an IPv6 connection.

How to really turn IPv6 off

1. On the Omada gateway
   Settings → Network → Internet → WAN → Edit → IPv6 → Disable IPv6 (or set it to “Disabled”).
   This stops the gateway from acquiring an IPv6 address on the WAN and from receiving IPv6 routes.

2. On each LAN network
   Settings → Wired Networks → LAN → Networks → Edit → IPv6 → Interface Type → None (you already did this).

After step 1 the gateway will stop forwarding any IPv6 traffic and the DNS cache will no longer contain IPv6 answers (except for any local or link-local traffic that never leaves the switch).