Jo's Squib error?

[Brenda]

No: HPFGUIDX 123721


Luckdragon:
On Jo's website under "Miscellaneous" she states that Arabella Figg 
never saw the dementors that went after Harry and Dudley in the 
alleyway in Little Whinging, however; at Harry's trial Mrs. Figg says 
she saw the dementors gliding towards the boys and goes on to 
describe them. Is Mrs. Figg lying or has Jo made another (Colin 
Creevey Camera) error?