interval pace only 10 seconds

Why it is not possible to set a pace interval (in custom workout - Distance, Time, Open) more accurate than 10 seconds?

I need to set (but every Runner does!)at least the pace on 5 seconds, for example 3 minutes and 45 seconds per kilometer.

I see a very fine setting with mode "Pacer" but it is limited on setting only the distance (and, of consequence, the time). This lack is really limitating.