I am not convinced that it's a DDoS attack, I mean who would do that?
More likely it's thousands of users, simultaneously trying to log back in, over and over again after something disconnected them, eg. a server problem.
GF doesn't really have any reason to lie about this, the first downtime which lasted for 5 hours happened very early morning and there were not thousands of people on at that time.
On the other hand that GF doesn't have proper DDOS protection and no server monitoring/staff at work during the weekends/morning on the other hand is the real issue here. Hopefully they learn from this incident.