An AMD Ryzen 7 PRO 4750U APU has been discovered on 3DMark. The reported base clock rate for the processor is 1,700 MHz while the maximum turbo clock rate is listed as 4,201 MHz. Unsurprisingly, these clocks would fit the Ryzen 7 PRO 4750U snugly between the Renoir APUs Ryzen 7 4700U and Ryzen 7 4800U. Lenovo will soon be releasing new ThinkPads with Ryzen PRO 4000 chips.
https://www.notebookcheck.net/AMD-Ryzen-7-PRO-4750U-processor-spotted-on-3DMark-could-soon-turn-up-in-new-Lenovo-ThinkPad-laptops.455408.0.html