It appears they are not quite the same. Little confusing for sure.
Supplement companies often use NAT instead of L-tyrosine because NAT is much more soluble in water.
N-Acetyl Tyrosine (NAT) is the amino acid tyrosine bonded to an acetyl group. The acetyl group must be removed from NAT to form tyrosine and become active in the body.
N-Acetyl Tyrosine Molecular Structure
Tyrosine is not very soluble, meaning it does not dissolve well in water. NAT is much more soluble than Tyrosine; because of this NAT is often used for parenteral nutrition (intravenous feeding) instead of L-tyrosine because solubility is crucial for infusion.
Source: https://www.prbreake...e-inferior-form