Exactly. References are here: https://forum.xda-developers.com/mate-20-pro/help/emui-9-1-partition-rw-t3947916/page2 and here: https://forum.xda-developers.com/huawei-p30-pro/how-to/erofs-mounting-accessing-img-t3944193/page2.I heard about this in the PM's. Would be interesting to find out more.
Only I'm not sure if we have anyone remained onboard who is able to customize 9.1 and more important 10.