"First" is awfully confident assertion about an event thousands of years ago. "Earliest known" is more accurate.
No matter what we do know, we can never prove there wasn't someone else who figured it out even earlier but never wrote it down, or they did but it and all references to it were lost.
Most "firsts" carry an implicit asterisk that isn't worth mentioning. The first person to run a 4 minute mile did so in 1954. With the asterisk that somebody else might have already done that millennia ago but didn't have a stopwatch. And we'll never know.
Kind of the same way you don't usually include the country code of your phone number when someone asks for your number (unless you're in an international context).
In all areas of life, we give technically incomplete information, but reasonably expect people to know what we mean. Because we're humans, not computers. And we do it all day long, every day.