I read it as a kind of test and first step for the always stubborn Israelites (Exodus 32:9, Isaiah 48:4) to return to God’s original Genesis 1:29 instructions, much like telling someone who refuses to be vegan to start by cutting out pig flesh from their diet. If they at least do that, then they have shown an inkling of willingness to change and have also proven to themselves that they are capable of change. If you look deeper into the requirements for eating even the clean animals, you see that they are literally impossible to follow, such as draining every drop of blood from the carcass (Genesis 9:4). So even when an Israelite would attempt to obey the instruction, they would knowingly fall short every time. But their willingness to drain most of the blood out is motivated by their faith, which is at least one small step toward obedience to God’s instructions. I would suggest reading Permission and Going the Extra Mile for a fuller explanation that ties it in with several other parts of scripture.