I think the shape has to do with diffusing the pulses of fuel returning to the tank. Folks who've replaced the 'cigar' hose with regular hose claim they've heard noises.

How can the return line in a W123 300D leak on the turbo? Even if it does, I don't think there's a risk of fire. But don't go trying now

Sixto
95 S420
91 300SE
87 300SDL
83 300SD