Thanks man, I did figure that was the case. Once approved I could then actually build the SBR. The videos I had all watched said you file the report with what you PLAN to build, then once approved bam you buy the parts and build it.
Living in MA, I'm used to submitting the fingerprints and all that anyway. So I don't mind that I'll have to submit passport photos, and fingerprints. I'll live haha.
I'm sure someone will correct me if I'm wrong, but with regard to constructive possession, the only thing that makes your rifle an SBR is the barrel, so you can begin sourcing all other parts immediately once you know what you want, just not the barrel. And that's if you're even worried about the minuscule chance you'd get jammed up on that kind of charge...