Changes to local dependencies causes long build times

Hi! I am trying out working with local external dependencies to share common code among several mongoose os applications. I am building my project using docker and the --local flag.
I have cached my libs and binary-libs externally to my project tree.
I find that any time I make a change to my common library that this triggers a a very long rebuild of all other dependencies.

I create a iot-common folder with a mos.yml in my project/shared folder.
I add it to my project’s mos.yml file as a lib:
- origin: shared/iot-common

I build with the following command:

mos build --local --deps-dir=/Users/user/Development/mos/deps --binary-libs-dir=/Users/user/Development/mos/binary-libs --verbose --arch=ESP32 --build-parallelism=4 --no-libs-update

The build succeeds however I would not expect changing 1 lib to require rebuilding of all other libs. Am I missing something?
If I change nothing my rebuilds are short <10s.

I am running mos 2.20 on MacOS.

Thanks!