Problem/Motivation
Similar to #2912731: Concurrent installing of a module is problematic but probably less problematic.
Concurrent operations that affect a sites configuration such as extension installation and removal and config import and maybe others don't work well with one another. Exporting the configuration at the same time might export an inconsistent state of configuration with no warning.
This is mitigated that in a typical setup each developer that changes configuration does so on their own instance of the site. Deployments then make the change all at once with a config import.
Proposed resolution
Locking? Documenting that this is not really supported?