Ben – in a word, aesthetics :)
While your method is simpler and may lead to a better finished product, it is nearly impossible to gauge the amount of foam needed to fill the ball without it billowing out and all over the leg and workspace. Â I had used foam in the past that stuck tenaciously and badly stained anything it touched. Â Based on that experience I choose the method I documented. Â Truth be told, the particular Dow foam I used on this project didn’t stick well and also didn’t seem to stain. Â Another reason is that the hole in the ball will need to be enlarged enough to fit the fill tube…I chose to make the hole as small as possible.
I had planned to experiment with the process you described if I ever had to rebuild the feet.