There is a lot of evidence to prove that the Needle Pistol once had this trait I described.
starting from 2:08
starting from 7:08
starting from 11:25
And this trait was clearly designed, rather than being a misapplication of the Mk II’s on-kill explosion trait. Because if you look closely, you’ll notice that the toxin radius of the Mk II’s on-kill explosion (three to four shoulder widths) is larger than the toxin radius on a direct hit (slightly larger than a shoulder widths). This shows that, at the code level, the developers not only specifically implemented an on-hit toxin-spread effect, but also limited its radius for balance reasons.
In the current version, there is still evidence that the Needle Pistol produces an AoE effect on hit. If you try it, you’ll find that it deals 1 damage in a small area, completely inherited from the old design—except it has lost the most crucial part: the toxin-spread effect.
Therefore, it can be clearly stated that such a design for the explosive mode did exist, but it was quietly removed in an update. (I’m surprised that the English video creators and English forums I’ve been watching have no reaction to and no awareness of such an obvious bug.) And I’ve been asking FS whether this was an undocumented intentional nerf or a bug that hasn’t been fixed yet.
If it was an intentional nerf, that would be pretty funny. As I mentioned earlier, the explosive mode’s current performance is extremely weak, and its usage rate is probably less than 1/20 of the primary mode—and that’s putting it mildly. Based on my own gameplay experience and a few Hive Scum H40 videos I’ve come across on YouTube, the usage rate of the explosive mode is roughly zero.