Good reply, though I do have a couple of new points, the first being that the seals before Jellal casts GC are way to low to in the air to be GC. Every time Grand Chariot has been cast the seals have always been noticeably high in the air (see Jellal vs Jura and Jellal vs Neinhart), it even looks different here in the next panel, the beams of light come from much higher than where the seals were. In addition, I didn't put my words well in the previous posts, I meant to say that they couldn't move
away from the Solid Seal, so sorry for any confusion there.
I don't buy Racer not getting out of there before GC struck either, we saw in a previous panel during the fight that Racer closed the gap between him and Jellal in an immensely fast moment, to the extent that he looks like he teleports to behind Jellal. If Racer can close that gap so quickly than he should have been able to get away from GC easily, yet he doesn't.
Edit: There's only six seals in the Jura vs Jellal panel, was it fully powered? Also credit for
@Linali for translating the raw for me and adding to this argument.