I’m aware of the Act as our Town had a militia at one point. There are many facets to its’ implementation and it wasn’t realistic. We had a small area where arms were kept but not until about 1830.....and not everyopne was required to “be there”. There were many exemptions...and there were also benefits.
I am willing to bet that gunpowder was stored there, but not individual arms. Back then, there was no such thing as smokeless powder and it was dangerous to store large quantities in a home. Often times, militias would also have firearms for those that were unable to afford their own weapons. Those are likely to be they type of arms stored centrally, and artillery if they had any.