Light is matter?

Matter = massive particles.

Light quanta, or "Photons" are not waves or particles. They are excitations of a Quantum field that can be approximated by waves or particles in given situations.

---

If we say that all 17 particles of the Standard model come under the banner of "Kishi", presumably then either;

Reishi consists of a similar, symmetrical set of 17 particles that mostly behaves in the same way (i.e. you can construct soul society out of it)

OR

Reishi consists of 14 particles which are symmetrical to all the quarks, leptons and weak nuclear bosons of the standard model, which interact in the same way as Kishi does with the remaining 3 boson fields; the Photon (carrier for EM, light); the Gluon (carrier for Strong Nuclear, it's what holds quarks together in hadrons and what holds nucleons together in nuclei); and the Higgs (the interaction with which gives particles their mass).

---

*wipes brow*. Onto the actual point of the question, light must have a soul due to the fact that when Fullbringers manipulate matter, they inherently manipulate the exchange bosons that hold the fundamental particles together. If they couldn't, then they would instantaneously ionize/de-nuclearize all particles whenever they used Soul Communication, and there would be explosive recombination as all the free radicals re-bonded. Logically speaking if they can manipulate exchange photons, they can manipulate 'travelling wave' photons.

---

But bleach isn't logical, and on-site it all comes down to balance. FBers could only manipulate light as part of a release because it's basically an illusion technique.