This one is rather technical and quite a long read, but there are two main take aways. Frass does give an immunity boost to the plants, and sterilising te frass does not mitigate this effect.
Frass: Immunity Boost
Full article
https://www.sciencedirect.com/journal/biocatalysis-and-agricultural-biotechnology
Reference
(Blakstad, et al. 2023)
Blakstad, J. I., Strimbeck, R., Poveda, J., Bones, A. M., & Kissen, R. (2023). Frass from yellow mealworm (Tenebrio molitor) as plant fertilizer and defense priming agent. Biocatalysis and Agricultural Biotechnology, 53, 102862-. https://doi.org/10.1016/j.bcab.2023.102862