NishmaBlog: Ruth, Geirut, Yibbum, Questions
We often presume current Halachah equates to ancient Halachah, but this is not always the case.
EG Erusin used to precede Nissu'in by about a year.
Here, too we may be witness to a drawn out "two step" process
This was a Conditional and Revocable Conversion [Gerut]
Ruth and Orpah were valid but temporary Giyorot with the right to return to their original status.
Similar to a Ger Katan or to a K'tanah who has been married
off by her mother or brothers. Both have a right of revocation when they come of age.
This is the joining of Am Yisroel permanently. While Orpah did a form of "Mi'un" by returning to Mo'ab, while Ruth accepted Israel and Hashem permanently. Apparently by doing so, she became a valid wife to Machlon and was entitled to a form of Yibbum
Possibly Ploni Almoni was concerned that Ruth still had the right of revocation - hence he expressed concen: "pen ashchit nachalati" OTOH Bo'az either realized that this was either not Halachically possible, or even if possible, that Ruth's commitment was irrevocable anyway.
Shalom and Regards,