use of cash is not prohibited, the proposal forbids it for amount larger than 10k in a single transactions unless authorized
A notary signing an agreement between a buyer and a seller is a legitimate reason to spend all that money in cash.
Which is very rare though, I only know old cow farmers in little towns close to the mountains here that deal with much cash (for lack of near bank offices and their lack of a driving license)
Yes, notary was involved and it would be invalid if buyer didn't paid, but it was very much a bundle of cash getting exchanged.