I guess I care about my cars more than others. I would never take my cars to any shop that would do that kind of damage. It's attention to detail. If they cause that kind of damage with simple jacking operation, makes you wonder what kind of work they do with the mechanicals. Cars should come back cleaned and vacuumed with no grease on floor or steering-wheel.
To answer the OP's questions, yes follow the manual:
1. if you have proper "
lift blocks" to support the pinch welds, then go ahead and use them.
2. otherwise use the frame-rails points, which are extra re-inforced beefy box-sections (blue).
3. for HF hydraulic floor jacks, use the cross-members (green). This is fast and balanced, and you don't twist body of car. Notice how doors don't close quite right when you jack up just one corner?
Another benefit of not damaging pinch-welds is rust. With such small contact-surface area, it's inevitable that you'll scrape off paint down to bare metal. Then rust sets in (see photo above), especially if you live in rainy/snow area. Before you know it, you'll have holes through bottom of body. With much larger contact-area and lower pressure on crossmembers and frame-rails, paint stays intact and no rusing.
