The genitive (as ablative) may denote that from which anything is separated or distinguished. On this principle the genitive follows verbs denoting to remove, restrain, release, cease, fail, differ, give up, and the like. Thus, διέσχον ἀλλήλων ὡς τριάκοντα στάδια, they were about thirty furlongs distant from one another, ἐπέσχον τῆς πορείᾱς, they desisted from marching, πολέμου ἡδέως παύσεται, he will be glad to stop fighting.
The accusative may denote extent of time or space. Thus, ἐνταῦθα μένει ἡμέρᾱς ἑπτά, he remained there a week, ἐπορεύοντο σταθμοὺς πέντε, they proceeded five days’ journey.
So…what are the grammar notes referring to here? The table of paradigms of the Aorist, Perfect, Pluperfect and Future Perfect Indicative Middle are all showing only the person of the verbs and the number of the verbs, organized after certain tense and mood of verbs.
The grammar notes relate to the use of the genitive and the accusative in certain of the sentences set for translation below the paradigms in sec. 189.
If a verb takes a specific case (or one case in one sense and another case in another sense ) that will be true irrespective of whether in a particular instance the verb takes the form of an Aorist, Perfect, Pluperfect or Future Perfect Indicative Middle etc.