If the idea is to allow traffic coming off the freeway and traffic entering the freeway to enter at the same time, the capacity for the on-ramp would seem to only be as high as the number of cars that could be stored in the loop section beyond the signal, something that seems to be of very low capacity, even for the loop with the double lane section. Further, the interchange is still limited in capacity by the overlapping off-ramp movements; even allowing simultaneous on and off ramp movements would not eliminate this other issue (something that would be solved with a DDI).
I would assume a DDI is not being used here because of the high levels of through traffic? It's not quite clear to me why they need extra capacity at this location. If there is an issue with left turn cycle length, I would think double left turns at the ramp terminals would be a more than sufficient improvement.