A misunderstanding of words then. To expand on snow's response and why we've used the terminology that way: we generally look at "DPS positive" to mean a gain over Dosis (or whatever other flavor of DPS slop each other healer has). Since Dosis can be cast in potentially every GCD from start to finish, we compare actions to how much damage is gained or lost compared to just casting Dosis. In that sense, we can look at Dosis as a 0, healing spells as a -1 and other attacks like E. Dosis or Phlegma as +1. Since Pneuma is the same potency, it also is 0, thus "DPS neutral" as snow explained.
I take your meaning is that anything that isn't a -1 is "positive" because you're still gaining the same amount of damage. Regardless, the reason why I do not consider Pneuma to be a part of Sage's DPS arsenal is because it being neutral means there is no reason to consider the damage of Pneuma (outside of AOE which isn't a particularly important part of FFXIV's design anyway). That means for what it's worth, Pneuma is effectively just "Cure III" only without the opportunity cost of damage. I wouldn't necessarily call Toxikon "DPS neutral" for the record except for your initial three casts, because any cast beyond the third requires you first lose damage by casting a barrier, and while there will be times where casting a barrier is necessary, those are extremely rare in most content because of how Sage's healing is loaded almost entirely onto its OGCD.
I think Toxikon would be a lot better if we gained an Addersting from something like casting E. Dosis instead.