
I've always seen "grinding" as doing the same tedious but simple thing over and over again in order to level up, like I felt I did in Portrait of Ruin before facing Dracula, and I've honestly never interpreted a different connotation from anything I've read, including your definition, which I feel I just more or less repeated here.
But then, as you might have guessed from a Castlevania game being my reference point, I just flat out don't play JRPGs very often, if at all, but I do feel like I grasp the concept and what people mean when they use that word.