Spullla's other option:
NE-NE, onto the copper. Yes, it's flatland, but only Argos units could possibly hit them there. Then, NE & threaten Argos, and the Thebes units won't be able to attack the stack (they'll be able to defend in Argos). With the catas suiciding, then Spullla could strike. Or camp on that forest, while their fast-movers run up from HR and burn down Sparta and Athens. It's not a fork, but a flanking maneuver: catch Jowy with his Thebian army out of position. While the other flank comes in and chops The Great Wall and such to shreds.
If they had brought 2 chariots, I'd have guessed they were going for this, to then cut the copper.
NE-NE, onto the copper. Yes, it's flatland, but only Argos units could possibly hit them there. Then, NE & threaten Argos, and the Thebes units won't be able to attack the stack (they'll be able to defend in Argos). With the catas suiciding, then Spullla could strike. Or camp on that forest, while their fast-movers run up from HR and burn down Sparta and Athens. It's not a fork, but a flanking maneuver: catch Jowy with his Thebian army out of position. While the other flank comes in and chops The Great Wall and such to shreds.

If they had brought 2 chariots, I'd have guessed they were going for this, to then cut the copper.