Buyer: Why is the vendor able to see revisions before I issue them?
The view contract page is currently a live look at the contract for both the buyer and the seller associated with the contract.
Revisions you make to an issued contract are available to be viewed whether or not you issue those changes to the seller; the only difference is when you issue the revisions, the seller is notified by email notification, whereas if you don't issue the revision, the seller would have to look at the contract unprovoked to see any changes.
There are some other minor things to note like the seller's history table will not show the detailed revisions like your view of the history does until you issue those revisions, but the seller will have access to the downloadable PDFs of any previous version of the contract just like you do.