"You can tell all that just from a rule of grammar?"
The grammar rules of different sign languages are similar to each other, but they aren't the same.
Our focus is more on actual communication than grammar rules.
However not probable, is held true in the English rules of grammar.
Within the rules of grammar, the writer can arrange words in many ways.
Following the interpreter pattern there is a class for each grammar rule.
And we will even have different sensitivities to the rules of grammar.
There's no easy way to do it except to study all the rules of grammar.
The two systems have different rules of grammar and some variance in vocabulary.
I stick to facts and teach the rules of grammar.