You probably haven't forced the RPi4 to support 4K60 modes in config.txt. The 4K60 modes are not enabled in RPi4 firmware by default, and to MatteN point most users have no need for them (the only media I see "in the wild" above 4K30 is test media).
I put hdmi_enable_4kp60=1 in config.txt, otherwise many movies are not in 4k 60 quality??