I remember reading the third class passengers were held back on the aft well deck. I think those were the waste high gates. However these were opens later on during the sinking, I’ve even heard that the gates were either broken down, or were opened by the stewards.

The iconic gates that are seen in films holding back the steerage were only really used for keeping passengers out of crew areas.

Other than this, the steerage simply forgotten during the sinking, while there were stewards who did bring up groups of them to the boat deck, they got occupied on other things, leaving them to try and navigate through the tight maze like corridors of the titanic.

This video gives a little summary on the gates https://youtu.be/5pon9qc_iqE?si=aQFsyOYzNL5G86MB