I, Joseph R. Biden Jr., do hereby grant a full, complete, and unconditional pardon to all current United States citizens and lawful permanent residents who, on or before the date of this proclamation, committed or were convicted of the offense of simple possession of marijuana, attempted simple possession of marijuana, or use of marijuana, regardless of whether they have been charged with or prosecuted for these offenses on or before the date of this proclamation
Not 100% sure what you’re arguing, but Presidents can and have issued blanket pardons in the past. Notably, Carter issued a blanket pardon during his term for anyone who dodged the draft in the Vietnam era. I’m sure there are other examples.
Importantly, presidential pardons only work for federal crimes. State crimes cannot be pardoned by the president, they have to be pardoned by a governor.