Using RequestContext::getMain in service wiring code should be avoided as documented on the core ServiceWiring.php and discussed in the declined T218555. In favour of T330109.
The service wiring in Vector skin is using the web request and the user to instance the FeatureManager.
It would be better to have a factory to get called from the skin with the RequestContext and creating the manager from that information.
This would avoid the technical debt with the request.