What is the reason for non-linear structure in many mishnayot?

Question

What is the reason that many mishnayot are structured in non-linear fashion, where the first case discusses Topic #1, the middle case discusses Topic #2, and the last case returns to Topic #1?

One example is Kesubos 6:5 which at first discusses the size of the standard monetary dowry, then digresses to discuss a case of no monetary dowry, then returning to the case of monetary dowry again.

Another example is Berachos 7:3, where at first the mishna discusses the view of Rabbi Akiva (as Tanna Kama), then digresses to discuss the view of Rabbi Yossi, and only then returning to discuss the view of Rabbi Akiva again.

It would seem more logical and efficient to place the digression at either the beginning or the end of the mishna. The standard answer given to almost all questions on the structure of the mishna, is "for memorization purposes," which may be true. Is there another way to explain the need for such a non-obvious structure?

Answer 1

Usually these questions are discussed by the commentators. The only case I remember seeing the reason for a Mishnah being written a certain way being given as for memorization is the first Mishnah in Megillah (see Rashi to daf 4b.)

I have heard that חיסורי מחסרא's, or cases of missing lines in the Mishnah were done for memorization purposes, but I don't recall seeing that in an authoritative sefer. I would look in the commentators for a better answer before defaulting to that one.

For example: The Mishnah in Kesubos is discussed by the M'leches Shlomo, who writes

מבואר הוא קשר משנה זו עם שלפניה דברישא קתני פסקה לו אלף דינר שהוא עסקא רבא ובתר הכי קתני פסקה לו כספים סלעא נעשה ששה דינרין דהיינו עסקא זוטא כדכתיבנא וקתני נמי בינייהו שומא רבא ושומא זוטא כדכתיבנא והשתא קתני דעני שבעניים לא יפחות מחמשים זוז אם הוא משיא בתו סתם ובתר הכי קתני גרוע שבכולן דהיינו פסק להכניסה ערומה ובתר הכי קתני דאפי' הנשאית מארנקי של צדקה דינה כעני שבעניים

Basically, the Mishnayos discuss cases in descending order in terms of possible dowries. The Mishna before discusses someone who says 1000 dinar, then just money in general. Next is the dowry for the poorest of the poor, followed by a case where there is no dowry at all. This concludes the list of possible dowries.

Afterwards, the Mishnah teaches that an orphan whose dowry is provided from charity gets at least as much as the poorest of the poor. Since it is not actually a category of its own, it is mentioned at the end as being part of an earlier category.

Another point I would make is that since the next mishnah deals with an orphan, it makes sense to put the case of the orphan at the end so that it will lead into the next Mishna.