I think that you are possibly missing the point, and why glue records exist …
The TLD’s that are problematic are problematic for a variety of reasons. Most on the list (such as .ca) require 2 name servers per the appropriate RFC. Most TLD’s have chosen to ignore this requirement unofficially - so they do not enforce is as .ca & .de do (amongst others). Others only allow the subdomains for the name servers to be in the format of ns1.domain.je which does not allow the MiaB standard of putting the name servers on a subdomain i.e. (ns1.box.domain.je) this is the case with .gg .je and .as.
Now the reason that we have glue records is so that there is an official place for the DNS system to check what the locations are for the name servers on a specific domain. IF you run name servers on a domain then there must be Glue records listed by the domain registrar. That is the only reliable way to identify the location of a name server as how can you find a name server if you do not know its address? So the glue record provides the official database of name server addresses.
Now a little about how name servers work. There are what is called ‘primary’ and ‘secondary’ name servers. This does NOT specifically refer to ns1 and ns2. It refers to the name server(s) that have the absolute OFFICIAL dns zone for a domain (the primary) and the other name servers who receive their information from the official dns zone, which are the secondaries yet still speak authoritatively for the domain. So to quickly summarize, the secondaries serve official records but they receive those official records from the primary name server.
Ok, so what happens here is called a zone transfer which is when the primary gives all of the secondaries the information needed to serve the records to DNS inquiries. The primaries always transfer to the secondaries - it is a one way transfer. They do not transfer elsewhere, such as to the glue records - because that is not the purpose of a glue record.
Now, in MiaB parlance, ‘External DNS’ refers to the fact that the name servers handled for the domain(s) served by our box are handled elsewhere - by a different provider … be that Cloudflare, the registrar, our VPS provider, whoever … and by definition since it is EXTERNAL, there is no glue record on our domain for it (it is not on our domain, so why would there be) AND by definition our domain DOES NOT need a Glue record because our domain does not have any name servers.
So … if we tie all this together, we will see that there is no correlation at all between using External DNS and having Glue records for our domain.
Which leads me to this question …
The answer is that it doesn’t. Having glue records on a domain which has no name servers does not ensure consistency. How could it?
So, in conclusion, I will state again - there is no reason to create glue records when DNS will be hosted Externally. And in some cases, due to rare malfunction (which would usually be caused by human error), it would be best NOT to have them pointing to an IP when they do not exist.