Dative example in Assimil L'allemand = mistake?

[Speakeasy]

Whereas the English case system has been largely supplanted by a more rigid word order than exists in languages still having a such a system, an analogous situation to the one above exists for some prepositions.

For example, a distinct (but now largely ignored) difference exists between “in” and “into” and “on” and “onto” or, at least, that’s was Grammar Girl continues to maintain. I agree with her, not only because she appears less dogmatic than, and nowhere near as fearful as, my 10th Grade Grammar teacher but, because she’s right.

Some differences in the use of “where” (whither, whence) are now considered archaic … um, er, to the rest of you … sorry, the forum does not have an Emoji for Old Fart.

EDITED:
Typos.

[jeff_lindqvist]

If a single phonological form acting as a preposition can take two different cases with different meanings, is this one word with two meanings or two different words? Discuss. (10 marks)

Inspired by an old HTLAL post (about nominative/accusative/genitive forms in Russian), I say that the words are different although they look the same.