Considering glider vs big bird ... consider the comparative differences in
(a) spoiler frontal area and contribution to total airframe drag
(b) aircraft mass
and the usual observations are readily explained ...
The value of spoilers on the sailplane is seen in reverse .. very clearly ... on the odd occasion when the glider launches with the boards cracked and the tug pilot then has his work cut out and, perhaps, an unpleasant decision to make ...