Why is this VDP not authorized?
The key is in the part of the procedure description I've highlighted:

When local altimeter setting not received use Northeast Philadelphia altimeter setting -- you're using the altimeter setting for an airport 15 miles away.

15 miles may not seem like a lot of distance, but it's enough for there to be a notceable variation in altimeter settings. The FAA assumes this error will be in the least favorable direction (i.e. your altimeter will indicate you're higher than you really are), and accordingly they take some precautions when you're using another field's altimeter setting.
In this particular case:


The decision altitudes (DAs) are higher.
Baro-VNAV (vertical guidance for your descent based on your altimeter) is not authorized.
The use of the charted Visual Descent Point (VDP) is not authorized.




The VDP is telling you "If you are on the approach path and remain at the MDA until over this point on the ground you'll be on the glide path to the runway" (or alternatively "You can plan a constant-rate descent that intersects the MDA over this point and you'll be on the glide path to the runway"). 

Using the charted VDP is specifically not authorized in this case because the nominal descent angle you will have passing through it counts on your altimeter being accurate and your aircraft being at the MDA. Since the MDA has changed and we're using a remote altimeter setting the location of the VDP isn't going to be what's shown on the chart. (For example, if you're 60 feet higher than you "should" be &amp; everything else is perfect the VDP moves further away from the airport to provide the same glide path at a higher altitude).  

Rather than charting several visual descent points (which would be futile anyway as you can't know the altimeter error portion of the equation) the FAA just says "Don't use it: Fly the approach until you have the runway environment in sight and then figure out your own glide path intercept based on the visual references you have."