Usually, though, lab-grown meat is actually meat. It's possible that it'd have to be labeled "synthetic" or "lab-grown" (similar to how synthetic diamonds are named), but claiming that meat is not meat is nonsensical.
This seems like a particular definition of "flesh" that's not particularly germane to meatness. Lab meat is made of the exact same animal cells that regular meat is, the tissue just happens to never have inhabited an animal. When we eat meat, we don't value the fact that the cells we're eating were once part of an animal, we mostly value the taste.
It seems to me that this isn't a necessarily property of meat but a contingent one caused by the fact that meat used to only be possible to produce from animal flesh.
>When we eat meat, we don't value the fact that the cells we're eating were once part of an animal, we mostly value the taste
You'd be surprised. We even have different names and preferences for different age stages of the animal, different varieties of the animal (regional etc), etc.
Those distinctions exist because of the perceived impact on the tastes and textures of meat. Not because of anything such as ethical preferences to old/young animals.
Diamonds are pretty simple from a chemical point of view, atoms of Carbon linked together in a particular structure. You can't compare something as complex as creating animal meat with creating synthetic diamonds.
A typical simple one is "animal flesh". Cells grown in a vat aren't flesh, they are a tissue culture.
Note that I'm not particularly animated by the issue, I just don't agree that it is as simple as "claiming that meat is not meat".