But this highlights the difference between the two devices, stopwatches and timers.

A stopwatch counts up. Therefore, it makes sense to use the floor (4.99 is still "4", not yet "5").

A timer counts down. Therefore, it makes sense to use the ceiling (3.01 is still "4", not yet "3").

In fact this was a turning point in the original article: "rounding down . . . makes a lot of sense when counting up. . . . But for a countdown timer, this is counterintuitive."