Well, that's not what the posted link shows. It just shows that their support is very slow. The problem was eventually resolved.

That's still not good, but I don't like clickbait.

Here's the workaround from the end of the thread:

"Remove your SPF records (just delete the TXT record) BEFORE going through the iCloud record addition/validation. This should fix it for you. Their validation system appears to be buggy and is not handling multiple include:statements properly."