Should an added dependency clear cache?

[vidartf]

I'm just exploring using this plugin for optimizing a webpack rebuild. This is for rebuilding an application after the install/uninstall of extensions to the application. As far as I understand hard-source, if you change the version of a dependency, you have to clear the cache (makes sense). However, I'm thinking that if you purely add a dependency, without any packages being updated, the cache could be retained.

Question 1: It that assumption correct (adding dependencies should be ok)? Question 2: If so, what can I set the environment hash to in order to use this?