The Secrets review measurements were taken in-room. While the reviewer has clearly done a pretty solid job of setting up his bass traps, that's not necessarily a cure for all problems and is likely part of the reason that the measurements were +/-4dB between 20Hz and 75Hz. Your room response is likely to be quite different.

The LFM-2 does not go down to 25Hz (well, it probably will in most rooms - after all, it hit 20Hz pretty comfortably in the Secrets review - but it's not rated that way). The LFM-1 has been discontinued and the LFM-1 Compact appears to be taking its place in the line, so it's not surprising that the two have comparable frequency responses. Keep in mind, though, that frequency response alone does not define a subwoofer. The LFM-1 was rated at 115dB of output while the LFM-1 Compact is rated at 112dB - the smaller driver and cabinet are tuned to go as low, but at a cost of 3dB of output.