Hate to be the squeaky wheel, but I found another issue with the Stormcast data.
Dracoth mount traits aren't showing up in the unit editing screen. This effects Lord-Celestant on Dracoth as well as Vandus Hammerhand.
Thinking it was maybe a keywords thing, I looked at the keywords for both units and noticed the Behemoth keyword in the Lord-Celestant on Dracoth unit as well as missing the Dracoth keyword. Vandus has the Dracoth keyword though, so that doesn't seem to be the issue.
@OftKilted Ah, gotcha. Yes, mount traits are independent of artefacts, though they are distributed similarly. Vandus and the Lord-Celestant on Dracoth are entitled to mount traits. The general mount traits (ones applicable to all mounts) shows up, but there is a Dracoth specific one that does not show up. I did a brief check on the other mounted heroes and it would appear everyone riding something that isn't a dracoth show both tables.