The only reasons I can think of are solid cams generally have higher lifts and shorter durations making the ramps a too harsh for a hydraulic to handle ... as well there's the increased valvespring pressure which will fight the hydraulic system.
He is asking about a solid lifter on a hyd cam so the ramp issue you talk about is a non issue, I agree with your spring theroy but that only requires the springs be changed ,
Comp sells/used to sell a set of hyd lifters that come with an instruction sheet telling the user to run .002 lash, I have a set.
