"777 pre-stall buffet on take off"
Before the newspapers get hold of this I'd very much suggest it wasn't any such thing.
I'd very politely and very much suggest
it's nothing aerodynamic at all and much much much much more likely to be nose wheel "shimmy" (a wobble/vibration as the wheel(s) spin downs) or something else gear/tyre related.
It's not that uncommon on many types, even the biggies, and yes, you do get it sometimes on the 777. If it happens it will be much more pronounced at higher rotation speeds.