I'm not sure why these different cases existed in the first place. They were introduced in rB53b01d90023a850b17ded5deb9cace354c8e298a a long time ago.
It's not quite clear to me why nodes should have different shadows when they are in a frame or not.
Old:
{F8780305}
Old with zero alpha:
{F8780307}
New:
{F8780303}
New with zero alpha:
{F8780306}