I was very fortunate in that the PO of my congregation took the view that elders were not authorized or encouraged to act like private detectives. The guy was the most powerful elder in the whole area (a large percentage of elders were people he mentored), so that attitude was pretty prevalent.
After I stopped going to meetings and moved out of town, he gave me one phone call and said he hoped I was doing well. When I started to give him my excuse, he interrupted me and said he wasn't calling to interrogate me. He was just calling to check in and make sure I was fine.
Because I knew him so well, I know that he mentally checked a box and for him the matter had been concluded. His view (and I know this because when I was a pioneer we discussed this issue specifically) was that the role for elders didn't begin anew until the inactive witness returned to the meetings, asked for help, or was otherwise in a position to affect the flock. Since I moved away, I've never even gotten one request for a shepherding call.
Since I fell off the grid, cut almost all ties with all JWs except my immediate family, I've never been bothered by them. I was doubly lucky because my immediate family has never confronted me or even asked about my going inactive.
Unfortunately, I think my case is quite rare. I know an elder from a hall not too far from where I grew up that would behave exactly like a private detective, going so far as to conduct "stake out" operations...follow suspsected evil-doers around to gather evidence against them.
As to the specific point in the letter, I concur with all the comments saying that it's unlikely to change behavior given how overburdened the vast majority of elders currently are.