Reference for Bekhorot 52:5

טעמא דתולש הא נתלש שרי

The same ruling applies if it became detached from an unblemished animal, that it is forbidden, and the reason, why [the Baraitha states] 'If one plucks', is to show the length to which Akabya is prepared to go, that in the case of a blemished sacrifice, one is evenly allowed to pluck it.

Jastrow