Logic Pro: 7.1 Support for Instruments

I am looking at a very strange phenomena that I can reproduce with JUCE’s Surround Demo Plug-In.
Logic Pro (11.1.2) only seems to recognize 7.1 as an output format for effects. NOT for instruments.
After adding this to the PIP in SurroundPluginDemo.h pluginCharacteristics: pluginIsSynth, pluginWantsMidiIn I cannot insert the Plug-In anymore as 7.1.
Only when I change Logic’s configuration to 7.1.(SDDS) I can insert the Instrument.
I am almost 100% sure this is a Logic Pro regression. It seems to be the same for NI’s Kontakt 8 at least.
Did anyone have a similar finding?

I am one step further. Apparently Logic Pro is able to insert the Instrument if you don’t specify any channel configurations at all. Just the number of output channels.
This works for Plug-Ins where there is no ambiguity in regards to the channel number. For example there is only 7.1 and not 5.2.1.