Instead, the first player does not get to see the opponent's cards before deciding how to summon the monsters.

This may not be a GOAT format thing; I believe it always worked this way at least according to the TCG, even if you look at the latest TCG text.
I believe even according to the OCG text it also mentions that both players reveal the cards first before anyone decides to summon. Also I checked the oldest Cyber Jar print with ChatGPT and it also mentions that both players reveal the cards first.

Video with the bug:
https://github.com/user-attachments/assets/ac8c20b2-e174-4ba7-ac57-0d74ef94b4fd

Old OCG Cyber Jar text:

I believe these two lines would need to be switched to achieve the expected behavior.