I would argue that taking an instructor or at least an experienced pilot as a passenger would offer some value for a portion of hour-building. I'm fortunate enough to have an experienced airline pilot and instructor as a father, and gained in my humble opinion a lot of valuable experience from having him sat next to me for a portion of my hours. We agreed he was purely there as a passenger/extra set of eyes and that I would be PIC, however any advice offered was graciously taken. I also flew a handful of hours with more experienced PPL holders and the CFI of my club, all valuable experiences.
Of course flying alone is also a big part of confidence building, so I'm certainly not advocating flying the entirety of the hour-building under supervision. I definitely believe a balance of the two is beneficial though.