Pd processes only output first two audio channels

[josephlarralde]

While designing a simple quadriphony spatializer, I noticed that Pd processes don't seem to output more than 2 audio channels.
I made the same algorithm in Faust and it works fine with a Faust process.
I'm using the same 4 channel output bus for both processes, and I specified the right number of outputs for the Pd process, which is supposed to stream sound out via an [adc~ 1 2 3 4] object.

I'm running OSSIA 3.2.0 on an M2 Mac with Ventura 13.5

Here are some pics to illustrate the undesired behavior.

This is the Pd process :

And this is the Faust one :