Multichannel AU mapping and allow discrete shannel layouts

Only if I do not allow discrete channels on isBusesLayoutSupported the channel mapping for multichannel (7.1.4) gets correct…

in my isBusesLayoutSupported:
if (channel_set_in.isDiscreteLayout() || channel_set_out.isDiscreteLayout())
return false;
if (channel_set_in.size() != channel_set_out.size())
return false;

Is there a way to allow also descrete layots and still get the correct channel mapping for AU plugins?

juce 6.1.6