Schizoid PD is a personality disorder which means it isn't supposed to appear (or be diagnosed) before adulthood.
I don't have the DSM diagnostic criteria in front of me ATM, but IIRC SPD doesn't require impairment in non-verbal communication, intense special interests, adherence routines, or stimming. There is probably more, but that's all I can remember off the top of my head.
Also, the name "Schizoid" is a holdover from way back when it was thought that SPD had something to do with schizophrenia. It is not longer thought to have any connection. (Seems like Psychiatry always wants to link everything the schizophrenia.)
So, there are differences, but I'd also say don't assume the DSM is some totally self-consistent system that will always make sense.