They are blatant samples.
If you want to get around the situation and just get the vocals, you can hire singers. That brings down the price of the sample to an interpolation, since the source track is not being used. That happens A LOT.
Since he raises the pitch of the singing, then the usage of hired singers which are a dime a dozen in LA or NYC, is all the much better business for him.
Clearing the sample, getting the master from the original owner is such a hassle, I really don't think that Roc-A-Fella would let him waste that much money when they could hire people to sing (if they wanted to).
However, West uses the samples ripped from their source, so the above doesn't even matter. Does it, really?
Sincerely,
God