Take a look at the choke butterfly plate. It might need a little modification. And yes the manufacture can mis-setup the carburetors.

There are times here that I must either close up or reduce the air bleed hole in the butterfly to increase choking action. At one time we had a lot problems with Tecumseh engines were we had to solder one hole for them the work properly. I even had a large UTV with a twin Subaru 650cc engine that I had to do this to as it was extremely hard to start during temps below 40f. I also got a generator with Briggs 210000 series engine that I had do the same on as it also refused to start during cool weather.

I also see case on a hand held leaf blower where it would start during the summer months because this. When I ordered a replacement carburetor the manufacture had over closed the bleed and engine would flood on the very first pull. I had to enlarge its bleed until I got a good starting condition. It took several days to do so as I had to make sure the engine was cold each time I tested the new config.

As test you can temporary block the bleed hole and see if this helps.