I did some testing on my end, and so far I haven't been able to reproduce this issue.
Since you have an environment where this is happening could you create a ticket with our team so we can check it out?
Wait... no ticket... instead, let's be clear on which server
we are making the setting changes.
I was making all these setting changes on the server creating the subdomain (the Solo server). But I re-read the description for allowremotedomains and it sounds like it allows OTHER servers to set up a subdomain for a domain it serves.
"This setting allows the creation of parked domains (aliases) and addon domains that resolve to other servers."
That's what I see in testing. If I set allowremotedomains=1 on the main domain's server it allows the other (Solo) to set up a subdomain for remote the main domain, and no setting changes on the Solo server are needed. Also if I reverse the scenario (setting up a subdomain on a multi account server, off a main domain on a Solo server) the necessary setting (allowremotedomains) IS available on the Solo server.
So it seems that allowremotedomains works as expected, and does not take into account whether servers are in a cluster, in that it allows or prevents ANOTHER server from creating a subdomain for an account it hosts.
BUT... consider how allowparkonothers works when I tested it on DNS clustered servers. You can set up a subdomain for a domain on a another server by setting allowparkonothers=1 on the server creating the subdomain, even though allowremotedomains=0 is set on the other (main domain's) server. Setting allowparkonothers=0 on either/both has no effect in preventing creation of subdomains between the two servers, if allowparkonothers=1 is set on the server creating the subdomain. (I tested this both directions and it holds true.) I tried this for a remote domain NOT in the DNS cluster, and that didn't work (as expected).
Not sure if we should call this a bug or a feature.
I assume allowparkonothers was meant to allow this where the scenario is between accounts on the SAME server.
"This setting allows a cPanel user to create an addon domain or subdomain on a domain that another user owns. For example, if a user owns the example.com domain, another user could create the store.example.com subdomain.
Setting allowparkonothers=1 on the server creating the subdomain also allows it create subdomains on OTHER servers in the DNS cluster even though allowremotedomains=0 is set. I assume because they are not considered remote since they are clustered, and may have been by design. If so, then it would still make sense for allowparkonothers and allowwhmparkonothers to be available on a Solo server. It allows the operation to be completed from ONE server, and it's a lesser concern IMO than opening up allowremotedomains. This would be especially true if all the accounts in a cluster were controlled by the same company/person, and they might want to leave allowparkonothers enabled, but definitely wouldn't want leave allowremotedomains enabled since it would allow any server to create a subdomain for a domain it hosts. (Or is it only effective within a cluster? This I couldn't test.)
If I am understanding this correctly, it seems allowremotedomains ignores DNS clustering, and allowparkonothers takes it into account, which seems a little odd.