In this first picture one can see where the gutter has been cut off at the same pitch as the roof to let the gutter empty onto the roof surface.
Gutter from one roof to another.
As part of this system malarkey recommends against the drainage of one roof directly onto another especially because the lower roof often has less slope than the upper.
The water is allowed to run on the roof surface and is collected by the lower gutters.
How effectively a steep slope asphalt shingle roof sheds rainwater is primarily a matter of roof slope and effective use of flashing including downspouts and gutters.
Note also that the valley also sheds its water down the roof surface as well as opposed to into the gutter.
Measure the area of each roof section to calculate gutter size.
A hole at the bottom of the gutter or an open gutter end will just splash water around in a heavy rain.