As an IT guy I cannot avoid the observation that the states "30-30" and "40-40", "deuce", have the same outgoing transitions in the state machine "tennis game": From both scores a two point difference is necessary to win the game, and the state machine degenerates to a machine with three states (advantage for either of the two players, or deuce). Likewise, "30-40" and "40-30" is "advantage" for the respective leader.
My son and I therefore started calling "30-30" "deuce" and "30-40"/"40-30" "advantage", first jokingly, and now as a matter of routine. As with traditional counting, a win requires scoring at least four times and being two scores ahead.
This habit does not change the game, right?
Edit to address closing as dup: The alleged duplicate is an entirely different question. It asks in effect why we don't count 1, 2, 3 instead of 15, 30, 40 but does not address the fact that there is no logical distinction between 30-30 and 40-40 (or 2-2 and 3-3, for that matter).