>that we haven't nailed down yet in replicating it, but we'll get there eventually

So that's not how this works. You can grind up the real muscle tissue and the fake muscle tissue and assay out how much of each amino acid and how much of each lipid type is in the sample.

At this point you can modify the genes for the lab grown cells until it has the nutritional profile you want. If it exactly matches the beef steak sample, it is nutritionally the same. It doesn't matter the path taken to grow it.