Your first sentence is not correct.
One wants to optimize D3 levels year round. I take a much higher dose than what you list to keep my levels at the correct level.
Anyone who wants info on vitamin D should check out the vitamin D council & John Cannell.
You are correct but to a newcomer, taking it at all in winter is a starting point.
Regarding dosage, there are those on this thread who will not begin with a massive dose. There is a learning curve
There are those here who scoff even though there have been many many long D3 threads with tons of evidence presented.
How can such a simple thing be real?