RTO certainly does deal with data loss. As long as your system is down, there's data you're not collecting. That is data lost.
RPO is NOT "how much data you can lose", but the specific point-in-time state (usually defined as an interval relative to the point of failure) to which you restore the database (Recovery Point Objective). Data loss is implied, not addressed directly, by this term.
Both of them deal with data loss. Neither of them deal with it directly. You can argue that RPO deals with it "more directly", but that's not really the point.