2. TRIAL PERIOD
Meiri provides the following explanation: “The rule to ‘examine them the entire year’ teaches us that even if they were examined at the beginning of the year... and they didn’t know {for Whose sake they took the vow,} if they utter a vow later {in the year}, we do not say ‘they have already been examined and they do not know.’ {Rather, we must question them again;} it’s possible that they’ve learned since and now understand. The same is true in the reverse: even if they knew how to vow properly at the beginning of the year and their vows were binding, if they make a vow later {in the year}, they must be examined again for their vows to be binding.”
In light of this explanation, we could propose that even though Rambam maintains that the Gemara reads (as it appears in our printed editions) “It might enter your mind to say... {in a case} where we examine her for thirty {days} and she did not know how to utter a vow properly,” he nevertheless holds that the rule (mandating examination) also works “in the reverse”: “even if they knew how to vow properly at the beginning of the year and their vows were binding, if they make a vow later in the year, they must be examined again for their vows to be binding.”
As to why he only references the scenario of “even if they knew,” {and leaves out the case when they do not know how to vow,} we can explain that he does this because this scenario contains a greater novelty than the principle that “even if they were examined... and didn’t know” they must be examined {throughout the year} (see above from Radvaz).
However, this explanation is unsatisfactory, no matter how you look at it: If this rule is indeed a greater novelty, then why doesn’t the Gemara mention it? By not mentioning this novel rule, the Gemara implies (as cited above from Kessef Mishneh) that “if she did know how to utter a vow properly (at the start of the year), she doesn’t need to be examined further (for she is established and presumed to “know how to utter a vow properly”).
