They literally did exactly that. That's what being cut off (Antigravity access, i.e. private "only for use with our client" subscription - not the whole account, btw.) for people who do "reverse engineer to use it in other tools".

Nothing here is new or surprising, the problem has been the same since Anthropic released Claude Code and the Max subscriptions - first thing people did then was trying to auth regular use with Claude Code tokens, so they don't have to pay the API prices they were supposed to.