When searching Digitec for Logitech M705 I got 4 articles, 2 of them have in the picture still a small Logitech radio receiver shown, the other two do not. May be that people who already have several Logitech devices at home already have several such receivers and dan buy the mouse without receiver. Without it is cheaper.
My Logitech M720 I can also connect without this receiver only via the Bluethoos. Then the mouse and keyboard reacts but only when Windows is started at Loginscren. If you connect them via the Logitech receiver so you can boot the computer even in the UEFI / Bios pure.