Mostly, I agree with what you have said. You will find differences in how they build however. Fastener sizes, air nails, hammered nails, clipped head vs full head, fastener type with PT lumber, nail patterns, blocking to support purlins that in turn help support trusses, vertical roof purlins vs "flat" roof purlins, PT lumber grade and/or treatment type, steel gauge, uplift ressitance on the posts, poured post pads vs precast, concrete around the posts or not, glue lam posts vs full PT, screw length and pattern, yadda, yadda, yadda. There is indeed a difference.
When it comes to pole barns, do not expect anything not in writing. Steel quage, trim, rat guard, overhangs, ridge vent, eave vents, door hardware, top and bottom, etc., etc. Your best bet is to ask to see other area barns built by the same builder if you are new at this.
Though I have seen alot of barns go up, it never ceases to amaze me how fast a good crew is. There is a barn going up near me that is maybe 40x80x16 high. It has gone from bundles of lumber on the ground last week to most of the tin on this afternoon. Hint: there are a number of workers with straw hats and women with bonnets serving up food among other chores. Tough to compete with that.