Granted. We know little about the accurate dimensions of the disc,
or even how to define precisely where the "surface" of the disc is. These stars must look more like spherical clouds, with fuzzy edges, not a sharp limb like our own sun.
No I was referring to the size of the disc, which in your original post you listed in "ly".
"...but Betelgeuse is 5.5 ly in diameter..."
I think you really meant "AU". No big deal, I figured it was just a typo. No star is light-years in diameter.
Stars are a few light-seconds across, the biggest ones like Betelgeuse a few light-minutes.