Osgi - Package Imports to Shared Services Benefits

Whenever a bundle gets updated in a OSgi environments the direct affect is that all bundles which have any import will also get bounced . This information is not displayed in the dm server console.
I have observed this change only by putting sysouts in the bundle activator. I feel this should not be hidden in the console.
This will also happen in the service model if the interfaces are bundled along with the implementation.
Bundle a -> Implementation & interface and provides Osgi service
Bundle c -> osgi service importer,has import for intercface packages from a
Now if we bounce the bundle a to change the implementaion bundle c also gets refreshed though we dont change the interface.
The only way to avoid this is to have a seperate bundle b with interface
Bundle b - > has interface
and now bundle c imports from bundle b , also bundle a imports from bundle b . Thus any changes in bundle a, thats the implementaion will not have any refresh of other bundles.