The ThinkBook 13x G4 has a 13.5" 2.8K (2880x1920) IPS 500nits matte 120 Hz display from BOE (the same company that has supplied all Framework panels so far) with rounded corners (and the rounded corners visually match the corners on the new Framework display).
Framework is probably using that exact same panel.
NotebookCheck tested that laptop to have a minimum brightness of 5.6 nits. Source