I think you know the answer.🙂
Milk is not blood.
Blood is the stuff in your veins and arteries.
Everything in the physical universe is made up of elements, atoms, molecules, etc. They move around and an atom of hydrogen that is part of a water molecule today may be part of blood tomorrow. The cells in your marriage mate today may be part of a different person years from now. Does that mean it's okay to have relations with that other person? Nope.
Kevin McFree might reuse some of his Legos for different scenes, but the discerning viewer knows the difference between a Wolf Elder Lego character and the Brian With A Beard character.
God knows it's possible to take blood and put it in a centrifuge and separate things out, etc, but just because you can do something doesn't mean you should do it. You can drink water from the public toilet if you want, but I wouldn't recommend it.
In ancient times, the requirement was to bury your feces and pour the blood back to the ground. In this culture now, we flush the feces away. Wonderful. The basic idea is still to protect people from getting sick. What's the deal with blood? If you do a blood test and then throw the blood away after, great. But to save it, separate it, sell it, stick it back in someone is obviously not "abstaining from blood." It's directly disobeying a clear command.
If the same types of cells are in milk, who cares? God said it's okay to drink milk. "The land of milk and honey." God knows the same types of cells are in a lot of things.
"Now the serpent was the most cautious of all the wild animals of the field that Jehovah God had made. So it said to the woman: “Did God really say that you must not eat from every tree of the garden?” At this the woman said to the serpent: “We may eat of the fruit of the trees of the garden. But God has said about the fruit of the tree that is in the middle of the garden: ‘You must not eat from it, no, you must not touch it; otherwise you will die.’” At this the serpent said to the woman: “You certainly will not die. For God knows that in the very day you eat from it, your eyes will be opened and you will be like God, knowing good and bad.” Consequently, the woman saw that the tree was good for food and that it was something desirable to the eyes, yes, the tree was pleasing to look at. So she began taking of its fruit and eating it. Afterward, she also gave some to her husband when he was with her, and he began eating it."
It didn't go well for Adam and Eve when they disobeyed a clear command. "You must not eat from it, no, you must not touch it" was clear. Even a fraction of that tree was off limits.
Adam and Eve just ate from a fraction of the tree. And look where we are today.
Jehovah's fixing it, but it's through the ransom blood of the Christ. We must show respect for that blood. The way we show respect is by respecting God's right to set boundaries. He set a boundary on blood. It doesn't matter if there are some of the same types of cells in blood as in milk. There were some of the same types of cells in that one tree in the garden as the other trees in the garden. It was the attitude and obedience that Jehovah was looking for, it was a way they could show love and respect for Him, and trust.
The GB/FDS doesn't trust Jehovah, so it's no surprise they would be misleading others into disobeying Jehovah. The snake did the same thing.