The March - December 2022 period proved quite unusual by historical standards. Although the employment level rose by more than 900,000 during this period, those employed full time actually declined by nearly 300,000, even as part-time workers soared by nearly 900,000 and multiple jobholders advanced by nearly 700,000.
A simple interpretation might suggest that service employees sidelined by covid returned to their jobs during this period, with some of them downshifting from full to part-time. Meanwhile, with price inflation running well ahead of wages for much of the year, many lower wage workers found additional jobs to help make ends meet.
Source: Labor Force Statistics from the Current Population Survey (LNS11000000, LNS12000000, LNS12500000, LNS12026619, LNS12600000)