I have read too much and want to verify if I am correct.

An AR pistol lower can be assembled into a rifle. But an AR rifle can not be converted to a pistol. Correct?

I don't want to SBR a lower that was sold with a pistol brace attached. I have configured as a 10 inch pistol but I would rather not fall for the ATF trap and just put a 16 inch barrel on it with a proper stock.

I already have 3 SBRs and don't really want another. The 10" barrel would be orphaned, unattached with no spare uppers. I should be able to justify it as a spare for the SBRs.