I was able to construct and use a raft long before I was able to construct a portal. I did so.

If wind direction was, in fact, influenced by portal location, how was the program able to set or change wind direction before I had built any portal?

I built my first portal at my base located on the western shore of my starter island. If the wind direction is most often from the nearest portal and I only had the one at my base, I should have had mostly clear sailing away from my base and had to do a lot of rowing on return trips. I do not recall this being the case.

Once I began to build portals on land masses away from my starter island, a consistent pattern should have emerged. More often than not, I should have started each voyage whether out from my base to a distant land or in from a distant land to my base with a tail wind. As I neared my destination, the wind should have changed to a head wind, requiring me to finish voyages generally by rowing. In my experience, this did not happen.