Indeed there was such a custom. Traditionally, the Babylonian annual Torah reading cycle with which we are all familiar had four "checkpoints" to keep everyone roughly in sync: Nitzavim before Rosh Hashana, Devarim before Tisha Bav, Bamidbar before Shavuot, and Tzav before Pesach. If you were in a small town and didn't have a calendar, as long as you doubled up portions as necessary for those checkpoints you'd be ok and you wouldn't have to calculate too far ahead.
Now, Tzav before Pesach is not so practical during a leap year, so the checkpoint for leap years became Metzora. The mnemonic here is (OC 428:4) פקדו/סגרו ופסחו מנו ועצרו צומו וצלו קומו ותקעו.
In years when Simchat Torah is just before Shabbat on Thursday, but Pesach starts after Shabbat on Sunday or Tuesday, there is that one extra Shabbat between them and we have to split something to hit the checkpoint. If that year is not a leap year, we split Vayakhel and Pekudei apart. If that year is a leap year, then Vayakhel-Pekudei and Tzaria-Metzora are already split and there is no other double parsha before Metzora to split. In that case, the common contemporary practice is to read Metzora two weeks before Pesach and Acharei Mot just before Pesach. The checkpoint fails, but what option is there?
One option is two split a 'non-traditional' section from earlier over two weeks. In Provence, there was a practice to split Mishpatim in half, with the second week picking up at Im Kesef. This is the practice you see reflected in the Chinukh who lived in Provence. This custom is mentioned by Avudarham.
