I really don't know. I've never measured the Icons. As I had to install my own graphics drivers I noticed that the desktop and taskbar icons were bigger with the default Windows drivers as the display size was bigger.
It's true, in Win 10 the task bar icons are smaller - I preferred them larger too! The new icon size is 24x24 versus 32x32 I think. Most applications don't include 24x24 so Windows is downscaling 32x32 icons (which loses some fidelity)
StartIsBack has the option to return them to the original size but I have yet to find a tweak or other program that does. I think SiB is hooking a .dll or something so as of now I don't think its possible.