I'm running Marshmallow and have a 64GB internal microSD card mounted as "adopted storage". When I tell TWRP (3.0.2-0) to clear the Dalvik cache, only a few apps (about 9) get regenerated ("optimized") on the next reboot. The remaining 100+ apps are not optimized on the next reboot. I've tried deleting the /data/dalvik-cache folder myself and get the same results. So, I assume that the oak/etc. files for the other 100+ apps are stored "somewhere else". Any idea where?
(PS: Yes, I know Marshmallow is an Art system, not a Dalvik system. The term "dalvik cache" is used in many places as a generic term to refer to the place where Android keeps optimized apps. Marshmallow still uses the /data/dalvik-cache folder for this purpose. Marshmallow's obviously just not as ... consistent about using it as earlier versions of Android.)