Right. I think of shardblade material (Tanvastium/Koravarium) as similar to dragonsteel as seen in Dragonsteel Prime-once shaped, or in this case summoned, it cannot be bent or damaged regardless of effort used (unless that effort is Nightblood, though that is more eating the Investiture than actually cutting it. (It's not a perfect comparison, especially for shardplate as at least dead shardplate is known to be able to be damaged by simple trauma and force)
Really? To me it seems like it's just a manner of how to channel the most investiture to the spren, shardblades are a literal physical manifestation of investiture and that's how Sigzil did it in Sunlit.
(I may be wrong though)