I don't believe they did constrain themselves in that manner. As the quote below seems to indicate, they allowed their research to go beyond the "Founding era"
"First, we reviewed “[t]hree important founding-era legal scholars [who] interpreted the Second Amendment in published writings.” Ibid. Second, we looked to “19th-century cases that interpreted the Second Amendment...”"
>it should be changed through that amendment process
I think we agree here. Not saying you hold this position, but there does often seem to be a bias for favored causes, though. E.g., constrained to using the amendment process when it comes to limiting gun rights, but no such argument when it comes to edicts that limit voting rights. I would just like to see consistency in thought/principle (again, not claiming you take a biased view).
>Perhaps because this was adding additional liberty
So just to stress test this idea, you would be in favor of any additional liberty that went through the amendment process? E.g., would you think it beneficial to allow citizens rights to nuclear procurement as long as it went through an amendment process? Or reducing the voting age to 10 years old? I.e., do you tend to think more liberty is always better?