I sharpen Step Blacksteel with 1/2" on my Sparx and there's zero issues. Also it measures the same both ways on my Sparx Edgechecker. I have regular Step Steel as well, and it's the same both ways.
Polished CCM Hyperglide runners I found had an issue with uneven sidewalls, leading to different readings front to back than back to front. Sparx has a note about steel with treated sidewalls in their manual for the Edgechecker, so it's a not uncommon thing to run into.
No experience with LS5 personally.
colins