That can be true of most battery chargers that don't have a lot of electronic hoopla, depending on the state of the battery.
I went out the truck last night and it was at 12.55V, BUT the lights were noticeably brighter when I opened the door and the diesel pickup started right up even though it's been 3 months since I touched it (other than putting the battery tender on for several hours yesterday. Given how warm the tender was, I'm going to venture that using a tender designed for Motorcycle and lawnmower batteries is probably is bit small when used on truck batteries (per the nifty instruction sheet I downloaded).
I also ordered one of these desulfators that was recently discussed in Mopar Action magazine. It was such a casual mention (in a tech article that was pretty low-key), that I almost missed it. I will post results when it comes in. Sadly: Only available from Chyna........
I'm still curious to see how it operates with only two wires.