Good points. Still, Sigzil is a particularly analytically minded Rosharan and even in these chapters uses terms like shade and Awakening to specifically refer to other invested entities/arts. I think Sigzil at least would use the correct term. Also, a Cognitive Shadow able to form as a physical shardblade/tool would be completely out of left field. I could buy something like a Seon doing it perhaps, but a Cognitive Shadow would be a hard sell.
But yeah, could definitely be a completely different thing from the Nahel bond we've seen so far.