This project gives a direct connection from the PA Turnpike onto I-95, where they cross. Otherwise, you need to take the PA Turnpike onto the NJ turnpike, which becomes I-95 but not until north of exit 6 - the entire NJ turnpike is not I-95. (Where the PA and NJ turnpikes meet, the NJ turnpike is not I-95 at that point - it doesn't become I-95 until several miles north.)
When I-95 was built, there were plans for an interchange with the PA turnpike, but at that time (1969) federal funds were not permitted to be used to connect an interstate highway to a toll road. That is no longer the case.
So what currently happens is that people exit the PA turnpike onto local roads, then pick up I-95 in Bucks County. Or vice versa - if you want to take I-95 north and then go west on I-276 (PA turnpike), you have to exit onto local roads then pick up the turnpike miles later.
I-95 is also disjointed in NJ. Going north on I-95 (forget the turnpike), it just "ends". You go onto local roads, and then pick it up again. This is part of a larger project to make I-95 continuous.
I suppose for historical reasons both branches are I-95. Although the New Jersey branch looks to be the “parent” route;
the Pennsylvania branch completes the I-295 loop (so it could be called I-295) although it is arguably a spur so it could get an I-x95 where x is odd.
Interestingly I-95 splits in New Jersey again between Ridgefield NJ and Newark NJ, with both branches called I-95. One ought to be I-x95, where x is an even number other than 2.