Another factor to take into account is that we do not find that the descendants of Keturah and Ishmael were sent into exile by Sennaherib, king of Assyria. Rather, it was Abraham who sent them away to the land of the east while he was still alive. Thus, the Rambam seems to be on very firm footing when he states that the descendants of Keturah are biblically mandated to circumcise themselves and would have to do so today if not for the uncertainty of their identity due to their dispersal among the descendants of Ishmael.
Nonetheless, it seems to be quite clear that in the Rambam’s view, the descendants of Keturah are not interspersed among the nations like other nations are.
(To be continued)