δηλοῖ δὲ ταῦτα πολλαχοῦ ὅτι οὕτως ἔχει
this is not a prolepsis but something similar in the sense that the subject of the rel cl is attracted to govern the main verb ( in prolepsis it would be the object). Is there a name for this construction?
This would be a kind of prolepsis too, inasmuch as there is grammatical “anticipation” of an element of the subordinate clause. That’s if ταῦτα is in fact nominative, as I’m inclined to read it (δηλοῖ intransitive).