athene unholy grail and galio? weird interaction?

Neither Galio's W nor Rammu's W is a shield. They're resistence steriods.

His "shield" is not a real shield, its more like a combat buff(+Mr&Ar) like a nunu w. Shields have specifc values, like morgana e, locket active, lulu/orianna shield etc. His "shield" is just a visual and is missleading.

shield = damage absorption, an extension of your health bar, typically gray.

galios bulwark = armor/mr buff