It's not possible to assign a ComponentGroup to more then one feature using <componentgroupref> </componentgroupref>
Light error:
[...]product.wixobj : error LGHT0095 : Multiple primary references were found for Component 'MyComponent1' in Feature 'MyFeature1' and Feature 'MyFeature2'.
Sample WXS file with two features
Turns out this was in the compiler. It was incorrectly setting all groups as primary when Components were defined there. Now it only sets primary when defining under a Feature.
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