This is interesting. I've always worked off the assumption that while english legal documents look like english they are actuallysomething a little special. These words get tested in court cases and opinions are written about them and what them mean. So, in this case my assumption (possibly incorrect) had been that each of those words had specific legal meaning, and perhaps a venn diagram would show 95% overlap of the sets, by using both words they get 100% overlap.

(Its also why lay people shouldn't write their own contracts, because a lawyer with contract experience won't use words that haven't been tested.)