I field-checked this today, and westbound does start at the I-95(12) ramp, but of course that ramp is currently closed.
Since the eastbound direction does not leave I-95 until Exit 13, I just ended the route at a new 13A point that I added to I-95 since the existing 14 point does not actually serve PA 291.
https://github.com/TravelMapping/HighwayData/pull/6762