Maharsha on that Tosfos asks this same problem.
בספרים שלנו אינו כן דויחל הוא אחר ד׳ פסוקים והקרבתם אחר ג׳. ועיין בתשובת מהרי״ל סימן קמט וקשה לי.
In our scrolls this is not so, for Vayichal is after four pesukim, and Vehikravtem is after three. See in the Teshuvah Maharil §149, but it’s a problem to me.
Well, let’s take a look in the Maharil, then. You can find this text online here at the top of page 8. The translation that follows is mine. I’ve translated some parts loosely where a literal translation doesn’t flow well, though I made sure to keep the inherent meaning of the words the same, and in places where I’ve added my own expansion on his words I’ve used brackets. I’ve also expanded his abbreviations.
וההיא דוהקרבתם לא ראיתי עליו תירוץ מקובל דדוחק הוא לומר דבימי הר״י היו הפסוקים בענין אחר מלדידן. וכל רבותינו המתחברים דבתראי אינון מייתי ליה. והתוספות בפרק יש נוחלין דזימנין לא היו בקיאין האמוראים בפסוקים וכן משמע פרק הפרה. ואם נאמר על רבותינו המתחברים צריך עיון.
And on that of Vehikravtem, I have not found an accepted answer, because it’s far-fetched to say that in the days of the Ri the pesukim were split up differently than ours. All of the Rabbis who compiled [the Sifrei Torah] later do not bring his [divisions]. Tosfos in Yeish Nochalin [write] that sometimes the Amoraim were not experts in the [divisions of] pesukim, and it’s similarly implied in Perek HaParah, but if you say this on the Rabbis who compiled, that requires further study.
שוב נתתי אל לבי דלמא מנהג צרפתי להתחיל פסוק והקרבתם בפרשת מוספין. ושוב מצאתי כן בתשובת רבינו תם אההיא דמפטיר עולה וזה לשונו וביום טוב קרו כולהו בעניינא דיומא והמפטיר הששי קורא והקרבתם עד כאן לשונו.
I later thought that perhaps the French custom was to begin [with] the passuk of Vehikravtem in the Mussafin. [Apparently he originally thought that we had the same minhag, leading to the earlier confusion of the division of the pesukim.] I later found in the responsa of Rabbeinu Tam similarly, on the topic of that Maftir Aliya, and these are his words: “On Yom Tov we read the entire topic of the day, and on the sixth day we read from Vehikravtem,” end quote.
אבל ויחל אינו קשה דכמה פיסקי פרשיות יש בספרי תורה של צרפתים דלא כרמב״ם [...]
But Vayichal is not an issue, for there are many divisions in the Parshios of the French Sifrei Torah which are not like the Rambam. [The rest does not relate to our topic, and so I conclude the quote here.]
In short, according to the Maharil, the French minhag was indeed to divide the parshios differently than ours, which are based off of the Rambam (as @DoubleAA correctly intuited in the comments to the OP). The Maharsha, for whatever reason, did not want to say this, so he left it as a question.
