From what I can tell is that this is for existing M110 SASS(KAC 20") guns still in service...not necessarily for the M110A1 CSASS. To be fair, the 3.5-10x was one of the weaknesses of the M110 system (others include the stock, suppressor...and potentially the trigger). The HK's are obviously still arriving in the DMR form with the 1-6 Tango Sig scopes. Not sure what the contract CSASS with higher magnification optic will show up with the S&B or what. It's the government/big Army...stuff rolls and changes. I wouldn't fret over it or break my neck to slap this on an HK clone job any time soon.
Currently Horus is fighting the Army regarding the reticle in that Mk5 Leupy. A very humorous thread on the hide about it.
TFB (which isn't really as on the ball as SSD most of the time) noted this:
"Note that the M110 rifle should not be confused with the M110A1 made by Heckler & Koch, which uses the SIG Sauer Tango6 1-6×24 scope. In case you missed it, H&K just did the first deliveries of the M110A1 Squad Designated Marksman Rifle."