Is Gathering Storm going to grant AD/AP faster in faster weekend game modes?

Gathering Storm is the rune used to replace the current "______ At Level 18" runes. But now that these stats are dependent on time instead of level, these benefits won't benefit anyone in the shorter game modes like Nexus Siege and Ascension.

Is it gonna proc more often in those modes, like every 5 minutes? 3? 2? 1?