Because absorption and bioavailability are complex thing and even few missing micro can alter the nutritional value whole; processed and synthetic for trend to miss out on that fairly often

Not automatically, but macros aren't everything, a lot of additives they add to make up for nature's magic tricks are concerning (I don't know about beyond meat specifically, but for most processed food it is the case)

If all that mattered in nutrition were prots, fats, carbs and sodium it would be muuuuuuch easier but sadly it's infinitely more complex than that.