While everyone has their own idea and what works for them, I see decreasing the speed or using practice mode (in between the speeds) as a hugely beneficial tool. I don't disagree that the different speeds changes multiple variables like @jhughes but the fundamentals stay the same. If a skier is very comfortable running 32 and has rarely or never practiced/ran 34, I think it is very unwise to immediately bump them into 34 because it is so different. Injuries could occur, frustration of not making passes, etc. but bumping them to 32.7 then, 33.3, 33.7, 34.2 is a much safer and gradual process while getting confident for those faster speeds.
As a coach of an elite sport (mens gymnastics) I just don't tell my students when learning a new (potentially dangerous) skill "go and try it and well see what happens and hope for the best, then we'll make adjustments from there". I won't allow my students to even try a double back flip if they can't do a single back flip. Then there are 100's of drills they could do before they are ready to even attempt a double back flip. Small progression steps give the best possibility for success. One small step at a time, master that progression (or close to mastery) and then move on to the next step. Pretty soon you'll have the new skill or pass. Obviously, the harder the skill or pass, the longer it takes to learn and more precise and consistent the student has to be.
Heck, I regularly ski the hovercraft at 19mph and it has helped me understand and learn many things that I apply to my 34mph passes.
Now I'm not an elite skier of even a good skier by any means but to say you shouldn't practice at a slower speeds because it feels different is not an accurate assessment (IN MY OPINION). Each pass builds on the next and going back to a slower speed or longer line lengths allows time to work on the fundamentals, which applies to every speed and length.
Everyone has their own method and finding out what your specific secret recipe for success is.... now that is the challenge.