you can skip that
it waits for the host to connect.
these days practically 'everything' is 'virtual' com ports, in Windows that is. USB isn't RS232 and it doesn't have any of the signals that is used in RS232.
at usb full speeds it is 12 Mbps (but this did not account for all the framing overheads etc) and that due to USB multiplexing, you won't get a straight 12 Mbps, that 12 Mbps is shared by all the devices and hubs connected. so if there is 6 of them (internal root hub, keyboard, mouse, etc), you get at most 12/6 ~ 2 Mbps at best. practically, every unused USB port is counted as well, so if a PC has say 6 of them, 2 Mbps is 'very optimistic'.
this is dramatically different from those 'Uno' style boards as stm32 do
*real* USB, not a 'crippled' usb tethered over a usb-uart dongle or chip.
stm32 can be turned into a HID device (keybaord, mouse, joystick, MIDI etc), or just about any USB device (USB mass storage, USB ethernet, USB wifi, etc. ). But it takes one's own technical prowess to get there. The 'default' setup (in stm32duino) only includes mostly USB (CDC) Serial.
as for uart on chip in the stm32. normally, those can be selected from the menu, e.g. to have them as Serial1, Serial2 etc so that Serial can be used for USB (CDC) serial.