Not if the average resets with the new tier. Then, a single 30 would result in a 60 average.
But this is fiction.
Truth is, the 57.87 ave. is safe to be the tier-up number because the player played some single rounds (not tournaments) as a TL until tiering up before the last score. This shows him as a "Champion" at the Par5 which does not initiate the count reset.
Taken a minute ago while the average is 57.87, the final TL number.