Plot Holes of Fallout 4 - Spoilers

[Dr Fallout]

Wasn't Vault 13 not getting enough water chips just a delivery cock-up, with Vault City ending up with hundreds and Vault 13 only one? Can't remember them ever mentioning anything special about Vault 15, other than that's where the NCR emerged from.

Yeah it was a mistake... I think. Vault 15 was a test on racial and cultural tensions, the vault had tons of different people put into a tight space to see the possible reactions from tension and hate.