+1
Spec wise, the GRC is more of a successor to the Celica GT-Four but from a model name, the GR Corolla is successor to the Corolla GT-S (AE86). IMO, it was just the timing from when Toyota announced the Toyota 86 as the successor to the Corolla GT-S based on some of the ingredients of the 86 in similarity to the GT-S; NA engine, 2+2, RWD.
The GRC has taken lineage of both the Corolla name, combined it with the Celica GT-Four specs and bundled it into one. A lot rumors flooded about the return of a Toyota Celica and here we are essentially witnessing it now.