It's a great pull, because it has an important implication that I think ties in directly to Nagels point. Another fascinating variation of the same idea is "beetle in the box", another great one from Wittgenstein. I don't think I agree with him, because I think it hinges on assuming lions have fundamental and irreducibly different experiences. But I think we have important similarities due to our shared evolutionary heritage, and even from the outside I'm willing to die on the hill of insisting that Lions certainly do have experiences familiar to us, like hunger, pain, the satisfaction of having an itch scratched, having a visual field, and having the ability to distinguish shades and color (though their experience of color is likely importantly different from ours, but overlaps enough for there to be such a thing as shared meaning).
I don't understand why Wittgenstein wasn't more forcefully challenged on this. There's something to the principle as a linguistic principle, but it just feels overextended into a foundational assumption that their experiences are fundamentally unlike ours.