The announcement protects the distinction
Rule 18 requires the player to make clear that a permitted second ball is provisional before playing it. Merely saying another ball is being played is insufficient. A non-provisional ball played under stroke and distance becomes the ball in play.
Imagine two tee shots finishing near each other after the first might have gone into thick rough. Without a clear announcement, the camera cannot determine the legal status merely by labelling the second image another try. The player’s communicated purpose matters.
Do not add both balls into one score
A provisional is used to avoid an unnecessary return if the original is lost outside a penalty area or out of bounds. It is not a free replacement chosen after comparing which result is better. Follow which ball remains relevant as the original’s status is resolved.
For a viewing note, label the balls original and provisional instead of first and second alone. That makes it easier to understand why strokes shown on screen might later disappear from the counting sequence when the provisional must be abandoned. The example explains the purpose and announcement; it does not replace the detailed rules governing when continued play of the provisional makes it the ball in play.
Questions answered
Is another ball always a provisional?
No. Its announced status and the permitted circumstances matter.
Can the player simply choose the better of the two?
No. The applicable procedure determines which ball counts.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.