For the DP-HDMI, it says “There are currently no DisplayPort to HDMI active adapters available that support HDMI 2.0 4K@60Hz operation.”
But for the USBC-HDMI, it says “enables an HDMI 2.0 output at resolutions up to 3840×2160@60Hz (4K/UHD) from systems which support “DisplayPort Alternate Mode (Alt Mode) via USB-C”.
What is the difference between “DisplayPort” and “DisplayPort Alternate Mode (Alt Mode) via USB-C” ? Can’t the chip used in the USB-C adapter be used in a DisplayPort adapter to do HDMI 4K@60Hz ? This might require the possibility of creating a DisplayPort (male) to USB-C (female) adapter that forces only alt mode signals on the USB-C side, otherwise an entire USB-C controller might be required. I think the VESA standard mentions a USB Type C to DisplayPort Adapter Cable which allows the DisplayPort side to be either a source or a sink.
Maybe the answer would explain why the TBT3-DP2X does 4K@60Hz but the TBT3-HDMI2X does 4K @ only 30Hz? Or is there a different reason?
BTW, those TBT3 devices are not listed in the RELATED PRODUCT / SERVICE list.