While it may be correct as per the defneition of the word, it's usage in that manner is (as far as I can tell) extremely rare if not non existent in the industry (embedded systems, computer engineering, microcontroller work, etc). Therefore, even if it is correct in the literal sense, it's usage this way introduces so much confusion (due to it meaning something else in those fields), it's effectively incorrect.
Quite the contrary, inside the field of computer science it is exactly the correct term used. Practitioners may use different words, but theoreticians describe protocols as instantiations of a language, whose encoding is defined by syntax. If you work on the formal verification of protocols, for example, as many people developing a spec would be, you would speak in terms of the properties and tradeoffs of various syntax.
