You can absolutely can vegetable soup! One caution don't put in cabbage broccoli cauliflower etc. It ferments the cabbage and it tastes like sauerkraut soup! ( lesson learned)It overtook the flavor of the whole quart!, just remember if you don't see on groc shelf it's probably not good to can. I have this yummy recipe mix of carrots, beans, onions, tomatoes, potatoes. That I can. On those cold nights when rushed I add my canned beef to it and YUMMY. Dinners ready. Some folks can all veggies separate also.
The advice of can as long as the longest vegetable is correct.
I have no idea why you were told creamed corn takes more time? That one stumps me.