Who said it was? They are different models; the 460 is more powerful. It is still an underlever. The 46 seems to be a rare model with a unique loading "port"; the 46 also had some problems.
I've got a D46. Very well made rifle. Not the most accurate in my arsenal, but it'll keep 'em within 3/4" at 25 yards. The unique loading gate is reminiscent of the Walther target rifles and the Webley Eclipse of days gone by. It's a nice sized, handy rifle that should be adequate for most airgun tasks. Here's a video that I made featuring my 46.