There are so many variables to consider when looking at suspected student paintings, that how about if we just pick a few obvious features that we can count on regarding positive ID for YST to start with..
We know that YST enjoyed large bottles to include clear, blue, and yellow.
There is a noticeable style for his painting of facial features, color palette, and horses, and warrior attire.
Just like any other bottle, we look at all the features and if there are more features that confirm a bottles date etc., than the number of red flags, then we can be put to some ease that we are on track for dating or confirming an artist.
The attached paintings I believe are straight forward YST style. Note the way the horses are painted, the large features to the warriors attire. I do not know the correct name for, but especially note the parts that extend the length of their arms.
The color palette is really straight forward with the exception that as
Bill points out he was also known to also use a much more vibrant color palette.
I think the bottle in your last post on the right is a good example for the above basics, and also your very first bottle in this thread, and as well this
bottle attached from Bills site. For me all three of these are without question YST just based on the few features mentioned.
Your bottle on the left shows completely different style of horses, clothing, facial features of which some were not even filled in, and as well the color palettes are off.