We should hope not, but that does not equate to infallibility. One bishop grants a nihil obstat and imprimatur on a book teaching the existence of purgatorial fire. This does not contradict the de fide Tradition of the Catholic Church, but that is not an infallible teaching. Another bishop grants a nihil obstat and imprimatur on another book rejecting purgatorial fire, and that likewise does not contradict the de fide Tradition of the Church. But neither is that an infallible teaching. The examples can easily be multiplied. In short, a nihil obstant and imprimatur does not equate to infallibility. In other words, absolutely no one is obligated to believe in something with the assent of faith from a book merely because it has a nihil obstat and imprimatur.
Bobzills. I ask this without any malice, but do so just out of a genuine desire to understand you. Do you have a learning disability? I am just wondering why it is so hard for you to understand certain concepts. If you do have a learning disability, please let me/us know, so I, at least, will not be so hard on you. If you do have a learning disability, then I would commend your questions. Otherwise…
Blessings