Basic functionality of level 3 maybe. Level 5 requires the car to make the right decision Everytime or else you don't have the basics. Basic of level 5 is level 5. Any functionality that is not fully mature is designated for lower levels. So the statement Elon made imo is optimistic and has missed his goal.
The "basic functionality" is the foundation, not the complete "thing" all sewed up and ready for use. You make claims that Elon did not, then point out that your claims mean it would be completely done. My apologies, but that is a straw man (however unintentional). Elon did not say those things, you did.
Think of it like this: you are going to make a suit. You get the cloth, the scissors, pins and the pattern. Depending on terms and intentions, this could be viewed as the foundation, but you are obviously not done. You pin the pattern to the cloth, and cut it out with the scissors. Now you have all of the pieces needed for the suit, but you still have to sew them together.
This is the point where I think Elon thinks FSD will be in "2-4 months". The "pieces" here are sign recognition, OCR (or functional equivalent, to get "55" into a speed limit), lane recognition, recognizing other vehicles, pedestrians, etc. The problem here, and why there are such widely varying opinions, is defining what constitutes those pieces that will be "assembled" into FSD.
My opinion is that Elon has again underestimated what is required to address the long tail and they will find that they actually need more capability in the "basic functionality".
Another point is that, unlike sewing a suit, you can't just glue those basic functions together. There are, as you rightly point out, significant issues with decision making. This is not easy and, as no one has done this before, no one really knows how hard it will be to do, or if it can even be done.
Now, if it can be done (and I think improving on typical human driving is definitely possible) then Tesla is clearly in the lead and with the best path forward.
In the end, I doubt we disagree significantly on this, but while I do not think Elon's goal will be reached in this time range I want it to be clear that what he is projecting is less than full FSD.
If none of that squares with your view of FSD, and that you cannot call it "basic functionality" without it being complete then simply recognize that your view differs from Elon's and translate it into terms you can find acceptable. But realize that he is *not* promising functioning FSD, but elements required in order to have functioning FSD.