Yes, these dlls are necessary.
If I remember well, with TDM compilers it was not necessary because those dependancies were statically linked internally.
Of course, if you have installed MinGW 8.1 compiler 64 bits, and the bin subfolder is in your path variable, it's not useful to duplicate them. But for a standard distribution, without compiler, you need them just for C::B itself.
gd_on