The primary-mirror of that one is reportedly spherical(per Celestron itself), instead of parabolic as it should be, at f/5. One tell-tale sign is that the primary-mirror is not center-spotted.
This sounds like superstition to me, or at least dangerously simplistic. Parabolic mirrors of course don't have to have a center spot, and spherical ones always could. Many which have been through the hands of an experienced astronomer likely do, even if it's just a paper ring. It may be less likely for a spherical mirror to come from the factory with a center spot right now, but I'm not sure I'd rely on that as an indication of the mirror figure. What you probably can rely on is that if a manufacturer doesn't advertise that their cheap Newtonian uses a parabolic mirror, it's probably spherical.