I dug around in the source and I’m not sure but I think that the spec in a Control is used when for instance you generate a gui using Ndef.gui. In that case, SC needs to guess what range to give a slider for a Synth’s Controls. So the spec inside a SynthDef is just indicating the range and warp factor of expected input, not modifying or scaling input as the Spec for a Slider might.
Someone else here may know better but that’s my guess!