Shop owner that I used to work for told me that Briggs OHV valve setting is critical to prevent kickback when starting. Anyone know if this is true and WHY? I don't understand how.

Yes it is, usually when the valves get out of adjustment, it'll catch on the compression stroke.

i think thats what my 14 hp was doing it would turnabout a half crank then sound like it hit a brick wall and just lock up. you would have to get it past the compression stroke and then it would turn over normal.