You most likely are running into the issue where this glass isn’t a thin surface shader.
Just to confirm: Try flipping the normals on that glass and see how the angle changes.
But in principle, either having volumetric glass, or using Backfacing to switch the IOR of the glass to 1/IOR on the backside should fix it.
AFAIK there also is a plan to allow Principled v2 to allow for proper single click thin surface glass.