A single separator is better than a choice of separators to mean the same thing.
A space is not as apparent in a large log of data as a capital T
Human language is not as strict as a programming language. There is a reason you see people still using “alot” and “a lot”. That just proves it’s easy to overlook and commonly happens.
I definitely don’t agree that the RFC is easier to read, the two numbers can appear to be one at a quick glance without a separator.
But there is a separator between the numbers: the same one that also very reliably separates the words in this comment