From the documentation- [Creating a Lightning Component for Use as an Action Override][1]:

> The Lightning Component Bundle menu includes every component that implements the lightning:actionOverride interface. 

>**A component that implements lightning:actionOverride can’t restrict an admin to overriding only certain actions, or only for certain objects.** We recommend that your organization adopt processes and component naming conventions to ensure that components are used to override only the intended actions on intended objects. Even so, it’s your responsibility as the component developer to ensure that components that implement the lightning:actionOverride interface gracefully respond to being used with any action on any object.


Also there is a known issue reported: [Filter Lightning Components when assigning Action Overrides][2]


  [1]: https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/components_using_lex_s1_action_overrides_markup.htm
  [2]: https://success.salesforce.com/ideaView?id=0873A000000CSRYQA4