That is exactly my point. The features of the lock were dictated by the selling price. Those late K export locks were made for sale in the US. You almost never see one in Britain* because there simply was no market for inexpensive fowlers. There was a market for inexpensive pocket pistols and there are thousands surviving.
Keeping in mind that there were no exports from England between 1774 and early 1793, it seems unreasonable to think that the continental suppliers didn't do everything in their power to fill the trade void. They were every bit as enterprising and as intelligent as modern merchants.
*I know of 1...on an export quality pistol marked to a county Yeomanry company...significant because the marking places it in Britain in period. So much of this stuff has traveled back and forth in the last 50 years that finding an example there hasn't much significance unless there is supporting evidence. That said, the inexpensive K pistols and fowlers we see at virtually every gun show are still unknown to British collectors.
And...I transcribed that from the hand written price list - which I own. Parts of it have been published before (but not the lock page) without my permission and, in at least one case, misinterpreted. The folks that "borrowed" it didn't have the rest of the Upson correspondence ... only a weak photocopy of the price list. I can say that the list was written out in August of 1812.
Here's a "best" quality K lock - with a sliding safety. I think the initials, BB
may be Benjamin Brazier - the first of the Brazier lock makers who were so prominent in the percussion era.