Neonchameleon
Legend
Every WotC pregen I can think of uses the Standard Array. If the rules actually do assume rolled stats there would therefore appear to be a lot of "do as I say not do as I do" going on from WotC.Neither of which have to do with the balance assumptions of D&D. The rules assume rolled stats, for balance. The array is a Mulligan a player can take instead of rolling, and point buy is a variant rule entirety. Neither is a factor to the game's core math.
Personally I think from observation that rolled stats in 5e are like a lot of the AD&D rules Gygax presented didactically and didn't use at his own table.