I am currently playing the seablock modpack and I can see this feature being useful in the sense that as soon as I have the production of a sciencepack setup I can research all the way to the next pack without utilising any of the technologies, where this update would be able to force me to produce the products of the new technologies before I can research more technologies.

From what I understood, they want to make it so that you can have those items in your hotbar without them being in your inventory.