Reference for Chullin 246:17

המפשיט בשרצים חבור עד שיפשיט את כולו הא בגמל אינו חבור

applies only to the case where he did not leave [untorn] a portion sufficient for an apron, but if he left [untorn] a portion sufficient for an apron, it [the garment] is deemed to be joined.

Jastrow