dig and host don't work in IPv6

[Andrew Schulman <schulman.andrew@epa.gov>]

Our agency has started using IPv6. My PC has IPv4 and IPv6 addresses. DNS
servers are all IPv6 addresses.

All of this works great, except that now the host and dig commands no longer
work, even with -6:

$ dig -6 cygwin.com

; <<>> DiG 9.11.9 <<>> -6 cygwin.com
;; global options: +cmd
;; connection timed out; no servers could be reached


It does work if I specify the DNS server in the command:

$  dig @2620:117:5010:1a1::f005 cygwin.com

; <<>> DiG 9.11.9 <<>> @2620:117:5010:1a1::f005 cygwin.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 56580
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1220
; COOKIE: d078f7e381ceee2117dbf35864c3e4d5b7b37dc8c646f48c (good)
;; QUESTION SECTION:
;cygwin.com.            IN  A

;; ANSWER SECTION:
cygwin.com.     3600    IN  A   8.43.85.97

;; Query time: 142 msec
;; SERVER: 2620:117:5010:1a1::f005#53(2620:117:5010:1a1::f005)
;; WHEN: Fri Jul 28 11:55:01 EDT 2023
;; MSG SIZE  rcvd: 83


It also works if I manually add a 'nameserver' line to /etc/resolv.conf. That's
not a sustainable solution though, since the nameservers change and I drop into
and out of the IPv6 VPN.

Should I be doing something differently? Or is it a bug?

Thanks,
Andrew