Daf Yomi Ketubot 52a: Levirs Redeeming Her and Receiving Usufruct

This is in all likelihood making way to much out of a typo, but there is a difference between our gemara's girsa and the Rif's girsa on Ketubot 52a:

{Ketubot 52a}
Gemara:

תנו רבנן נשבית אחר מיתת הבעל אין היבמין חייבין לפדותה
ולא עוד אלא אפי' נשבית בחיי בעלה ואח"כ מת בעלה אין חייבין לפדותה שאין אני קורא בה ואותבינך לי לאינתו

הלכך לית להו פירי דכי תקינו רבנן פירות לבעל תחת פרקונה הוא דתקינו והני כיון דלא מיחייבי בפרקונה לית להו פירי
תדע דהא תנן אלמנה ניזונית מנכסי יתומים ומעשה ידיה שלהן ואין חייבין בקבורתה
אלמא דכיון דחייבין במזונותיה מעשה ידיה שלהן וכיון דאין יורשין כתובתה אין חייבין בקבורתה
הכא נמי כיון דלא מיחייבי בפרקונה לית להו פירי

The Sages learnt {in a brayta}: If she was captured after the death of the husband, the brothers-in-law {our gemara: orphans, and we should probably emend it to match} are not obligated to redeem her.
And not only this, but even if she was captured in the lifetime of her husband and afterwards her husband died, they are not obligated to redeem her, for I do not apply to her "and I will return you to be my wife."

Therefore, they do not have fruits, for when the Sages instituted fruits for the husband in exchange for her redemption, and these, since they are not obligated in her redemption, do not get the fruits.
Know this, for we learnt {in a Mishna}: A widow is provided for by the assets of the orphans and her handiwork is theirs, and they are not obligated in her burial. Thus it is clear that since they are obligated in her provision, her handiwork is theirs, and since they do not inherit her ketuba, they are not obligated in her burial. So too, since they are not obligated in her redemption, they do not receive fruits.

The difference is that Rif (at least in our printed texts) speaks of יבמין, levirs, while our gemara has יתומין, orphans.

The Rif adds all the explanatory text which mentions orphans,

הלכך לית להו פירי דכי תקינו רבנן פירות לבעל תחת פרקונה הוא דתקינו והני כיון דלא מיחייבי בפרקונה לית להו פירי
תדע דהא תנן אלמנה ניזונית מנכסי יתומים ומעשה ידיה שלהן ואין חייבין בקבורתה
אלמא דכיון דחייבין במזונותיה מעשה ידיה שלהן וכיון דאין יורשין כתובתה אין חייבין בקבורתה
הכא נמי כיון דלא מיחייבי בפרקונה לית להו פירי

which is not present in our gemara, so this would seem to bolster the view that what we have is a mere typo, and that the Rif himself also had yetomin in his version of the gemara. On the other hand, he could be extrapolating this principle from the earlier discussion in the Mishna and gemara, and applying it to this case of levirs.

Indeed, a yavam pre-marriage we might say is exempt from redeeming her from captivity, for the zika does not extend that far. And we might deduce it from the Mishna which stated for a regular Israelite that he writes or does not write to her that ואותבינך לי לאינתו, "I will return you to me as a wife." For the levir was at no point a husband to her that his marriage to her would be returning her to her status as his wife.

We might also consider that based on the nusach earlier in the gemara, and in another gemara, we should expect hayorshin chayyavin rather than hayetomin.

We would have to compare this will halacha as ruled in other places to see if this is plausible in the slightest.