Whenever you use HC-05 to connect to a PC two COM ports are allocated to it. You connect to one of them (not either of them). Simplest way to explore this is with the Arduino IDE.
Maybe one is data from PC to HC-05, the other for data from HC-05 to PC. I don't know.
It appears to be a quirk (rather than an actual problem) that is exclusive to the Windows Bluetooth handler. It is not universal, in fact I have never seen it. This is because I use a Dell laptop, which uses the Toshiba Bluetooth manager. This could be commonplace with laptops, which have Bluetooth as standard equipment, while PCs usually don't, and maybe those users fail to add a decent manager when they plug in a Bluetootg dongle.