Why does Books ignore multi-output audio devices and aggregate audio devices?

I like to play audiobooks through my laptop speakers and a Baladeo bluetooth speaker. To do this I created a muti-output device using Audio MIDI Setup. Music, Firefox, VLC, Steam, Steam Games, Matlab, Voice Memos, the Microsoft suite of applications can all output audio through both speakers when using the multi-output device. Books only sends audio to only one, the master device. I tried making an aggregate device same issue. Why does this happen? Can it be fixed?

I've alrady turned to a third party app which allows me to access and play my music and audiobooks from one program (Not allowing Music to play audiobook files is a bad choice in my opinion). But I'd still like to know what's going on incase I come across it again.

I'm on a M2 2022 MacBook pro 13" running Monetery 12.5.