Not an exception really, there are many simple languages and Oberon-07 (the dialect linked) is indeed an extremely simple one. Go is another language that is simple. And of course C (that compiler developers abuse undefined behavior to win artificial benchmark games and making the life of everyone using C for practical purposes miserable is not a problem with the language itself but with the compilers that do such abuse).
This depends on if you see Oberon-07 as a different "version" of Oberon or as a different dialect belonging to the same family. Personally i see it as a different dialect instead of being the same language exactly because it removes functionality and isn't compatible with it.
It may not seem like a big difference, but it becomes more apparent when you consider how different all the Pascal dialects that are out there - some even from Niklaus Wirth himself - are.
Also IMO languages should not break backwards compatibility.
Wirth — at the age of 85, no less! — is actively working on Oberon stuff, like the compiler. Here's his "news" file, which is up to date as of May 31, 2019:
EDIT: Scheme too, at least up to R5RS.