In terms of net emissions at the exhaust? Beneficial. You don't have full load on the turbine, which means that you need to burn less coal until the plant has to pick up the load.
Problem rises from the sum of all things, not just the fact that renewables need nearly 100% spinning reserve backing them up because of their inherent unreliability. In example I list, the problem lies in the method of financing renewables, which basically ignores their real cost, both in terms of real CO2 emissions cost of having them in the grid as well as real costs of keeping them in the grid.
But to be fair, that sort of slack was always needed for novel technologies to be implemented. The problem is that we're simply nowhere near where we need to be on wind power and solar power in terms of longevity of parts for wind and relative efficiency for solar for them to be truly meaningful.
But it's also true that if we don't build them at all, we're not going to progress. This part of environmentalist argument is factually correct. The problem is the extrapolation of this argument into absurd levels, which is what is happening in Germany.