Hi,
That is an interesting experience.
Do you combine either of them in your actual application code?
Spring for configuration or MP Config, and which version of Jakarta EE?
In some like Wildfly 19 you might get them in sync because it already has Jakarta EE 8 and MP Config 1.4 while the earlier versions like Wildfly 18 were a mix between the pre Jakarta version of MP Config and an otherwise optionally Jakarta EE 8 compatible implementation, so you may end up with two or more separate "Enterprise stacks" if you even added Spring to your application ;-O
So regardless of the namespace question and if it's possible for a future Jakarta EE X (not necessarily 10) version to include a MP Config or other MP Y version, the timing is important. And if you look at the JCache JSR, that also is quite popular and has a few implementations but for the same reason it missed the inclusion into the Java EE (and now Jakarta EE) platform so many times, its Spec Leads don't seem to care about this inclusion any more.
Because JSR 107 uses the JCP in theory even a Jakarta Spec/API might use it but I am not a patent lawyer to tell all the nasty pitfalls, for your application you sure can use it, but it never made it into the Java/Jakarta EE platform so far.