This is interesting because without knowing how their system is architected or designed, it allows you to state assumptions and you can use that time to assert

This is interesting because without knowing how their system is architected or designed, it allows you to state assumptions and you can use that time to assert knowledge of best practices of a given framework. Sort of an implicit test for depth though. Edit: I missed where you said open source company. Though I still think this thought for a closed source company that uses open source pieces (like a web framework) could be useful.