i think is bc of susano it self it didnt say about the weaponsDude, that page is AFTER susano'o has formed. Go back to the chapter of susano'o forming and you will see how long it takes
1. StartsYou must be registered for see linkswith simple chakra
2. Chakra starts developingYou must be registered for see links
3. Finally the yataYou must be registered for see links
4. Still noYou must be registered for see links
5. Susano'o throws the sake from the gourd to form theYou must be registered for see links
6. Now the sword isYou must be registered for see links
Read the databook if this is not clear to you. Kishi does mention that the sword is created from the sake in the gourd according to the legend of susano'o and yamata no orochi
See above