I’m not an engineer. That said, just by looking at a frame it seems CS bridges have some utility in added strength to the / lateral rigidity in acceleration and strengthening the bottom bracket area. The webbed buttresses surely help some, too (only applicable to under the BB cable routing which seemed to have been introduced to save cash). Just looking at the basic geometry..
I also read somewhere that the CS bridges were helpful when used in conjunction with horizontal dropouts as a ‘limiter’ to keep the rear tire from jamming between the chain stays on some bikes during fast tire changes.