doesnt work that way friendo - as seen here with the Runeblade sword nerf thread - scaling and snapshotting was nerfed within a few weeks on top of blue post without any vanilla era evidence
TLDR - no one knew for certain whether it scaled or snapshotted in Vanilla as the only evidence found was from TBC onwards and yet decisive action was taken by the devs to nerf it.
Same thing applied to the Blessing of Sacrifice + Reckoning nerf several months ago
PS never mind the fact that we have no idea when the video’s footage was actually recorded, it’s upload date is Jun 28, 2006 - Patch 1.12.1 went live on 26 September 2006 - besides I only see ONE double crit within the batch window with multiple attempts over the course of the video.
That leads me to suspect that the one crit he got was just that, nothing more than a spell crit on the shock itself - if each successive Elemental Mastery cast with Chain Lightning + Shock double crits were shown then by golly you would have something.
Alas you don’t - sorry fam