When at least one fixed column is set in the grid, the stroke for this column is always visible to the bottom, when a horizontal scrollbar is visible:
If there is no scrollbar visible, this stroke isn't visible:
This should be consistent (always show stroke, never show stroke) or at least there should be an option for that, as that behavior is a bit weird in my opinion.
I think the intention was to make clear, that the fixed column(s) aren't scrolled?
Or maybe there is an option and i didn't found it? :-D