There is a bit of confusion around the word "understand" here. It is sensible to think of an object as "understanding" a message or not, but in fact the selector that tells you whether an object understand a message is #respondsTo:, while the equivalent on the class which tells you whether instances of that class understand is the one that's actually called #canUnderstand:. Other Smalltalk dialects simply say "ReadWriteStream does not understand #selector", no "a[n]" or "Instance of". (I like the use of present tense "does not" instead of past-tense "did not", as well, but that's a much more nitpicky personal preference.)
This is in fact already what you are doing with your class-side example, as `PragmaMenuBuilder class` is in fact not the class (that's just `PragmaMenuBuilder`), but the class of��the class, itself an instance of `Metaclass`.