maybe querier makes more sense but not an easy word to remember how to type

What would be the use case for exposing this?

Users just trying to work with query manager more directly, like especially when you are trying to use a specific engine.
One example is even testing a query-engine plugin directly.

Otherwise, I can do this, but it just felt awkward:

@pytest.fixture
def query_engine():
    return ManagerAccessMixin.query_manager.engines["etherscan"]