According to tradition the instructions there were dictated to Moses by God Himself.
The LORD called Moses and spoke to him from the tent of meeting, saying, “Speak to the people of Israel and say to them, When any one of you brings an offering to the Lord, you shall bring your offering of livestock from the herd or from the flock. Leviticus 1:1-2
So, do you suppose God really cared precisely how turtle doves or young pigeons were sacrificed to Him?
If his offering to the LORD is a burnt offering of birds, then he shall bring his offering of turtledoves or pigeons. And the priest shall bring it to the altar and wring off its head and burn it on the altar. Its blood shall be drained out on the side of the altar. He shall remove its crop with its contents and cast it beside the altar on the east side, in the place for ashes. He shall tear it open by its wings, but shall not sever it completely. And the priest shall burn it on the altar, on the wood that is on the fire. It is a burnt offering, a food offering with a pleasing aroma to the LORD. Leviticus 1:14-17
Because when I really want something to be done a particular way I repeat the instructions.
But if he cannot afford a lamb, then he shall bring to the LORD as his compensation for the sin that he has committed two turtledoves or two pigeons, one for a sin offering and the other for a burnt offering. He shall bring them to the priest, who shall offer first the one for the sin offering. He shall wring its head from its neck but shall not sever it completely, and he shall sprinkle some of the blood of the sin offering on the side of the altar, while the rest of the blood shall be drained out at the base of the altar; it is a sin offering. Then he shall offer the second for a burnt offering according to the rule. And the priest shall make atonement for him for the sin that he has committed, and he shall be forgiven. Leviticus 5: 7-10
If I were the omnipotent, omniscient, perfectly good, transcendent, immanent, timeless, eternal, personal Creator of the cosmos I'd like to think I'd have better things to worry about. Or, just maybe, the Book of Leviticus would make perfect sense...