It's more that, since you need blood, muscle tissue, and fat, (and probably more stuff) you need something to support their growth, you can't just create an homogeneous mass.
The GP is quite unimaginative to think you would need an entire animal for supporting those, but "some kind of fast growing meat cell" is wrong too.
> The GP is quite unimaginative to think you would need an entire animal for supporting those, but "some kind of fast growing meat cell" is wrong too.
What you described is actually pretty close to what I had in mind. I think you'd need something close to an "entire animal," since animals don't typically have lots of extra organs and systems they don't actually need.
If you start with muscle tissue and "add back in" all the stuff you'd need to grow it as a passive lump that just gets fed, I think you'd come pretty close to an entire animal: heart, lungs, and circulatory system; bones and bone marrow; kidneys; a digestive system and liver (because do you really want to feed it exotic growth factors); a rump of a nervous system; etc.
The GP is quite unimaginative to think you would need an entire animal for supporting those, but "some kind of fast growing meat cell" is wrong too.