Question: Verifying a Coin’s History

[cemozerr]

Why does a coin receiver need to verify the whole history of the coin they are receiving? Can the receiver not look at the newly published plasma cash chain block to see that now they are the receiver of this coin?

Is it because they can’t look at the plasma cash chain blocks, and so they need to look at the commits to the main chain and verify inclusion and non-inclusion since the genesis of the coin?