Yea. I think the OP makes it difficult to stick with a strictly biblical context as it applies an image God applies to "that day" to "this day".The OP. Was focused on are goats made into sheep as a poster had offered.
I believe scripture indicates the sheep were given to Jesus in what is referred to as the Covenant of Redemption. The number of the sheep is eternally fixed.
I can only suppose the poster was trying to avoid this reality with a novelty not found in scripture.
If he or she notices the thread perhaps they could clarify what they meant.
We cannot speak of "goats" becoming "sheep" because "goats" are those found not to be "in Christ" "on that day" and at Judgment is too late to convert.
All we can speak of are lost becoming saved and those saved being the "sheep" for whom Christ died.