Wishes and prayers are pretty solid building material in this setting.
Topically, the opposite is also true. Flying Grief house when?
Juubey was a drone corpse with two Grief Seeds stuffed in it. The Incubators as a whole are definitely capable of things that it isn't.
Kyuuubey states that Juubey couldn't cleanse soul gems because cleansing soulgems isn't under the purview of an Incubator's abilities-- it was an experiment that appeared to work, but that the Pleiades were unable to falsify. It's actually probable that Juubey actually
could to an extent, using the Grief Seeds the Pleiades gave him (which would be why they lasted as long as they did, given their heavy magic use and slow-burning Grief Spiral), but the cleansing
ex nihilo was merely an illusion. Other than that, it seems to share all of Kyuubey's innate properties
except for the power to grant Wishes (which was deliberate).
I think don't it is simply "Kyubey wants more Witches soon" since they're fighting universe decay, inpatience isn't their vice. So while it is correct Incubators try to provoke Witchouts anyways, siccing two novice Meguca who are just as likely to kill as they are to emotionally destroy their targets... Not really efficient, if the goal is merely "More Witches".
There's also the fact the Pleiades were already planning their whole "rejection" (which involved blocking out a whole city from contracts and seed retrieval) when Anri and Hijiri became Meguca in the manga, which isn't the case here. So unless the Pleiades have something they're definitely working on, it seems more likely Hijiri made her Wish due to similar events as the manga: Seeing a Magical Girl & Witch fight.
Kyuubey is an opportunist who benefits directly from making contracts and from girls taking SAN damage. He is a professional emotional predator who views his marks as particularly intelligent cattle and is unable to feel guilt or remorse for his actions. He's polite, cordial, and occasionally even extremely helpful, but at the end of the day his only true motive is to forestall Heat Death, and the most efficient way to do that is with the souls of teenage girls.
Hijiri seeing the fight (and her double) raises a lot of questions, which Kyuubey is obligated to answer in the most unhelpful way possible-- not only due to his policy of "Honesty" towards Potentials who pierce the Masquerade, but because he knows that no matter
what Hijiri wishes for, it's going to absolutely
devastate Niko, which further undermines the large regional power bloc. If Niko and Michiru witch out, he's pretty quickly got 7 witchouts on his hands as the Pleiades implode on themselves and an area ripe for a turf war which opens more opportunities for both witchouts and new contracts.
Bonus: By manipulating her while she's furious, terrified, and otherwise vulnerable, Kyuubey can turn her into a more direct weapon against the Pleiades, giving him cause to introduce her to Airi, a (at least marginally) senior Puella Magi whose entire
raison d'etre is FUCK THE PLEIADES.