Form is relative to your leverages primarily,& then the secondary factors include: strong/weak muscles,joints,ligaments, tendons, athletic ability which consists of flexibility and agility/acceleration.
Most people either don't lift heavy enough to know what proper from is, let alone instruct other people about it. Also these same people are typically so narrow minded that they limit a "complex" & diverse movement such as the Squat to one specific function for :
Geared powerlifters rarely walk out the rack, use both high & low bar placement and usually super wide leg stances and cut depth high, flat shoes, squat slow speed,
For Raw powerlifters it is usally walked out with a medium/lower bar placement,more medium stance, and a medium parallel or just below depth uses small heel/flat shoes, squat slow to fast speed
Olympic Lifters walk out, high bar placement, narrow-medium squat stance, low to high heeled shoes, squat very fast speed
Bodybuilders vary from body builder to body builder, as some of these other groups will have diversity as well, but typically do it very slow contracted speed, depth ranges high to low, stance is almost always narrow,medium at most, knees almost never pushed out, bar placement is high more reps then prior 3 groups listed, shoes vary but rest assured you will mainly see construction boots, otomix shoes, & stupid air/shock/pump type shoes
Cross-fitters will use running shoes, cross trainers, chucks, barefoot, vibrams, etc...
Typically will do more reps then a body builder would since they focus on endurance.
So the range of reps goes from all groups mentioned so far from :1-3, 1-5, 1-3, 5-15/20, 3-20+ for the most part if you stereotype the groups.
When you think how complex the list I mentioned before really is, so is the movement when you dissect them for example :
Add in Squatting on boxes (varying heights), Squat variants i.e. Front Squats, or different Squat bars, SSB, Buffalo Bar, Cambered bar, etc...adding chain/band tension, or lightened method,etc... and all other variables change the form for the Squat as a movement goes.
So all this being said taking in account the many different dimensional variables I think the first person to perform the movement or the first time a person performs a movement it is usually is I am going to get *Insert the following here*
bigger,faster,stronger,healthier,leaner,attracti ve) by doing this movement. How to achieve any one of said variables though, depends on other variables aside.
So there for it is safe to say "I LIFT THINGS UP, I PUT THEM DOWN!"