v.129 - Mark of Honor: Kanna Update Notes

From my direct experience, it doesn't reduce the spawn time but it does increase the spawn numbers. The test was at the Toy Room. The toy room is 4 Twisted Jesters on the standard spawn tick of every 10 seconds. With the two demons playing catch having been summoned, the spawn changed to 6 Jesters every 10 seconds.

I really hope this works at Castle Golems.

Ahhhh I noticed this too and thought it was odd that they have worded it wrong.
It certainly makes levelling an easy mode.
With Shoukan, Holy Symbol, other exp modifiers and Monkey Spirit (if you are a kanna) you would be levelling insanely fast.