A study is a data point- the results are collected by certain sensors in a certain population at a certain time using a certain method. If we understand the limitations involved, the data is useful. The question is not whether or not the information is 'true' but whether or not it's relevant to our question. With the limitations that have already been brought up (and the limitations of sEMG), this study is simply not relevant to the question of whether or not the bottom bosition of the LBBS engages the hamstrings, and thus can't be used in the argument.
There doesn't need to be a conflict between research, biomechanical analysis, and experience.
If I'm reading you right, you're implying that 'stretch' is equivalent to 'activation.' Using sEMG, you'll find that you can record some of the highest EMGs for a muscle off of a maximum voluntary isometric contraction. A muscle that is contracting isometrically can still apply incredible force- it's just not enough to move anything. Even if the hamstrings don't stretch much (and therefore don't see the benefits of the stretch-shortening cycle, which are usually hugely overstated anyway), they are certainly 'activated' as long as the hip-extension moment is high. They're hip extensors ... so this seems intuitive.