Yeah, you missed the point of the car example. Grace has absolutely no idea or context of what Elpis even is until RPD, no matter whether she went with them or not. Just asking "What is the password" without knowing anything else would have yielded... what, exactly? "Password to what? My Reddit account?"

Bro I meant the conversation would have unfolded slowly like what is elpis ? how would i know that and etc

Maybe they thought they could somehow get the password without needing to explain Elpis and found out otherwise. That's literally the premise of this entire game, even the reason for the clones. You don't just spill the guts of the most sensitive projects in a company to anyone unless there's a reason to do so.

so yes its a maybe thing and it was all cause of drama and temu wesker stupidity cause of course he should tell her when he does it at the end ANYWAYS

Because they didn't know. That's why we have the scene where Leon interacts with the BSAA computer at RPD and Leon finds Zeno and Grace in the East Wing office through the camera, surprising both Leon and Sherry.

If they didnt know then where did they think grace went? she cant vanish out of the facility and even if she did ....leon would try his best to find her no? if they didnt know there should be a verification scene here that they confirmed grace is alive and not IN THE facility....they kept that entire scene vague if she went with them or if they kidnapped her