J lock is a solution to a non-existent problem.
Just something for feel good legalese to cover manufacturer's butt.
Like Correia, I too can lock a 870 up so fast with no tools.
As Lee shared, no place for these on a serious shotgun.
I have seen and heard of hunters and even two gunsmiths snicking these on. The hunters did not have the tool to unlock the gun. Hunt ended early.
The gunsmiths - one had a tool from another gun to use, another had to run down the road and borrow one.
In serious competition, big money on the line - I and others removed the safety all together. It was legal, just had to inform RO and SO same as if one shoots release triggers. When one bird is worth $500, or maybe even $2k...serious shooting, serious money on the line.
I have a brain, and adhere to 4 rules like most of us . NONE of us every had a ND using a shotgun with the total safey removed on purpose. And I am speaking about folks that have run hundreds of thousands of rds thru a shotgun.