This summary is not the rule. The rule text controls.
If someone writes a will in another country, state, or U.S. territory, that will can still be accepted in Louisiana courts even if it doesn't follow Louisiana's normal rules for wills. The key requirement is that the will must be signed by the person who made it (the testator), and it must be valid under the law of the place where it was written, or valid under the law of where that person legally lived at the time.
To get this kind of will approved in Louisiana, you need to provide the same proof that would be required to validate it in the place where it was made, or in the testator's home state or country. In other words, Louisiana courts will look to outside law to decide if the will counts, and they'll expect you to show the same kind of evidence that place would require.
This rule matters most for families dealing with a death when the person lived abroad, moved between states, or had connections to more than one place. It gives some flexibility so that a valid will isn't thrown out just because it doesn't match Louisiana's usual format, as long as it followed the correct rules somewhere else.