I don't get it. If the logo is in the public domain, then how can its use be restricted?
They used exact same Bitcoin logo, changed color with tilt, and they said it's their own unique logo design

This would be like if I use any public domain logo, ...
Yes, and I believe there is nothing wrong with that because it is
public domain.
let's take for example well know Olympic rings logo by Pierre de Coubertin, change color, tilt it and call it my own unique creation.
That's a bad example because the olympic logo is a trademark, where the bitcoin logo is not.