This isn’t a new position for Biden with regards to his presidency. Here’s his statements on it over 4 years ago in Feb 2020:
Biden’s campaign told POLITICO that in his remarks on the recording, he was simply “restating his cannabis policy,” which includes eliminating criminal penalties linked to marijuana, erasing marijuana-related criminal records and “letting states set their own policies regarding legalization of recreational marijuana while further effort is made to study the effects of cannabis use.”