It means the Android operating system does not implement the DHCPv6 protocol.
> How is it impacting users?
Users of Android devices will be unable to obtain a managed IPv6 address configuration, other configuration, or request an IPv6 prefix (read: prefix, not address) via DHCPv6 Prefix Delegation.
> Are they crying out about it on support forums for the past several years?
For at least 10 years now[0].
Mobile devices typically (read: by default, and if they don't people will berate them for not caring about privacy) randomize the DHCPv6 DUID and MAC address used for the connection, meaning that one might as well just assign a random IPv6 address from the given prefix. Which is exactly what you get without DHCPv6.
The only people demanding DHCPv6 in Android are network admins still under the strange illusion that DHCP somehow gives them some kind of "management", "accountability" or "logs". They didn't get the memo that they will still have to correlate their 802.1x auth with the current device mac and IPv6 addresses in use, which is in no way whatsoever helped by DHCPv6.
You seem to be completely ignoring the other aspects of DHCPv6. Your response comes off as extremely hostile towards others who may have different requirements than yours. Please consider that there could be other use cases beyond what you've been exposed to in the past.
And what might those other aspects of DHCPv6 be? That it is an ugly misdesign that doesn't even do what DHCPv4 does? That e.g. MAC-address-based address distribution is against the DHCPv6 spec and either a broken oversight or a design flaw? That DUIDs are either a privacy nightmare or useless crap? Which use cases should I consider there, pray tell...