This is a bit of an exaggeration. Rich Hill is pitching no different than the slightly above replacement level pitcher he's been over the past few years. Contreras is the same as last year, intriguing stuff but still walking way too many and not striking out what his stuff would indicate. Oviedo and Keller have taken steps forward, but still no better than mid-rotation pitchers.
Then, on the position player side, you have Reynolds who is a true star, but otherwise you have a bunch of veterans and lower pedigree young position players playing out of their minds. For instance, McCutchen has suddenly started hitting like it's 2014, and Connor freaking Joe has a wRC+ approaching 200...
Better than the past couple of years, when they were really bad? Sure. But an up and coming team? It remains to be seen.