Modern MX starting technique (Pros)

Ricky Johnson said, "There are two major important parts to a race. From the start to the first turn. And from the first turn to the checkered flag."

Can someone give me a breakdown of the modern/current MX/SX start techniques the pros use.

I've noticed a trend where the rider quickly slides forward, then backward. Maybe to time with shifting? Is it to prevent looping out?

Start techniques appear familiar to my time in the late 90's, but so different at the same time. 

There are so many aspects to getting a good start. I imagine the pro's and mechanics analyze every last detail to get it right. What are those details?

• Mental preparation - focus and stress control, breathing, confidence, commitment, start routine, nutrition, supplements and smelling salts, mind games with your competition, injury mitigation and recovery, ADHD meds
• Bike preparation and technology - traction control, ECU mapping, tire selection, holeshot device, rear holeshot device, special gearing, suspension setup, clutch technology, 4 strokes vs. 2 stroke, gripper and bump seat covers, Factory vs. Privateer resources
• Unique track factors - Dirt, moisture, altitude, start surface (I know most all pro events start on grates but even that must have some variables), what is in front of the gate (ruts, rocks, soft spots), First race of the season vs the races in a season.
• Gate Selection factors - shortest distance to first turn, Left vs. Right first turn. 90° vs 180° first turn, LCQ vs Main Event
• Skill - reaction time, throttle control, clutch control, braking, turning, bike humping (slide forward/backward), practice techniques
• Call an audible - Change of plans in real time. How to adjust? James Stewart was so good at getting a bad jump out of the gate, but then sneaking to the inside and getting the holeshot
• Rider positioning - seat position, pull your crotch/pants tight, throttle over-grip
• Tenacity - solo practice starts vs 40 riders on a gate who all want that holeshot money
• Study - dartfish, slow motion, telemetry data, bio-telemetry data, lessons from Gary Semics (I'm old).
• Secrets only the pros know or make the effort to use? (Mike Alessi would study the gate timing and know to the millisecond when to go). Keeping the tires clean and warm (MXGP)
• The Future - electric bikes, Audio-cued clutch release, on the fly engine mapping, real time wifi updating, signal hacking, blood oxygen saturation, mechanical doping

What makes a rider so consistently good at starts? (Jett Lawrence, Mike Alessi)
When a rider works on starts during the week, what are they working on? (Haiden Deegan last week)
Why can't every rider replicate what works, and get a good start? (Mike Larocco)