My point is:
If a greenhouse is not a tangible and undeniable benefit then it is a lot of extra effort to create a more cumbersome farm (small walled-in sections that are hard to navigate) for a might-be gain.
In my current game I started a farm early and kept it going when I swung by the base.
It's not winter, yet, and I have almost 50 stacks of grain and maybe half that in veggies. Also some 25 stacks of charcoal because trees will not grow in winter, either.
If you work on food / coal at the start of the game then a greenhouse - that you can not build at this point - is irrelevant.
In the current situation / implementation, the greenhouse is a late game luxury or creative building item.
Something you build for showing it off, not because there is a gameplay reason to.