Maimonides the literalist

This piece theorizes as to Rambam's motivation in interpreting a pasuk as well as codifiying it in a way that can be seen as contravening the Masorah

The Torah grants both a father and husband the ability to annul a wife and daughters vows, respectively. 

All agree that a husband's rights are limited to nedarim that pertain to עינוי נפש ודברים שבינו לבינה.

Sifri and Yerushalmi, with the rishonim following suit, limit a father's powers of annulment to the same categories as a husband. 

There's a lone dissenting voice, you guessed it, none other than Rambam's, that differentiates between the two, giving a father unlimited scope in his control over the validity of his daughters vows. 

His language is as follows (nedarim 12:1): כָּל הַנְּדָרִים וְהַשְּׁבוּעוֹת הָאָב מֵפֵר בְּיוֹם שָׁמְעוֹ. שֶׁנֶּאֱמַר (במדבר ל':ו') כָּל נְדָרֶיהָ וֶאֱסָרֶיהָ. אֲבָל הַבַּעַל אֵינוֹ יָכוֹל לְהָפֵר אֶלָּא כָּל נְדָרִים וּשְׁבוּעוֹת שֶׁיֵּשׁ בָּהֶן עִנּוּי נֶפֶשׁ אוֹ שֶׁהֵן בִּדְבָרִים שֶׁבֵּינוֹ לְבֵינָהּ כְּגוֹן שֶׁנִּשְׁבְּעָה אוֹ נָדְרָה שֶׁלֹּא תִּכְחל אוֹ שֶׁלֹּא תִּתְקַשֵּׁט שֶׁנֶּאֱמַר (במדבר ל':י"ז) בֵּין אִישׁ לְאִשְׁתּוֹ. 

The Chachmei Lunel queried him regarding this. Rambam responded that it's a great question and that he's given it a lot of thought but as a dad's limitations go unmentioned in the tosefta and both talmuds (he is taken to task for overlooking the yerushalmi), and although נדרי עינוי נפש are the same by both and presumably dont need to spelled out separately for dad, however דברים שבין אב לבתו are very different from דברים שבין איש לאשתו, and should have been described, the fact that they were not makes it's safe to assume that the sifri is the lone opinion of R Shimon, it's author, but that it wasn't the consensus. 

Also, says Rambam, peshuto shel mikra doesn't support it, as although by a wife the Torah mentions the limitation of עינוי נפש (Bamidbar 30:14),  by a daughter it explicitly says (ibid:6) וְאִם⁠־הֵנִ֨יא אָבִ֣יהָ אֹתָהּ֮ בְּי֣וֹם שׇׁמְעוֹ֒ כׇּל⁠־נְדָרֶ֗יהָ וֶֽאֱסָרֶ֛יהָ אֲשֶׁר⁠־אָסְרָ֥ה עַל⁠־נַפְשָׁ֖הּ לֹ֣א יָק֑וּם וַֽי"י֙ יִֽסְלַח⁠־לָ֔הּ כִּי⁠־הֵנִ֥יא אָבִ֖יהָ אֹתָֽהּ maximally expanding a dad's power of cancellation. 

The other rishonim and poskim disagree  with the vilna gaon writing (YD 234:110) וא"א לדחות מ"ש בהדיא בספרי וירושלמי. 

As for Rambam's issue of omission, R Hirsch and Torah Temimah both say that actually נדרים שבינו לבינה are the same for both the husband and the father. As dad has an interest and right in marrying her off, he wants her to be as attractive to potential suitors as possible, with דברים שבינו לבינה actually meaning precisely what they mean vis a vis a husband, namely, between her and a potential husband, not her father. 

At the end of the day it seems that as Rambam elevates the literal sense of the Torah above all else, with only those (barring 3-4 cases, as he wrote in a responsum) counting as biblical (ShM 2nd Shoresh), contra Ramban, who has a more midrashic understanding of peshuto shel mikra (ibid), he simply cannot bring himself to accept something that goes against (his) plain reading of the pesukim, especially as it is omitted from many authoritative sources, allowing him to cast it as an opinion of R Shimon's only.