Ranged weapons without values for "short range" category

Question

The handbook for AD&D2e has the following to say regarding the range of missile weapons (emphasis mine):

The first step in making a missile attack is to find the range from the attacker to the target. This is measured in yards from one point to the other. This distance is compared to the range categories for the weapon used (see Table 45 in Chapter 6: Combat). If the distance is greater than the long range given, the target is out of range; if the distance is between the long- and medium-range numbers, the target is at long range; when between the medium- and short-range numbers, medium range is used; when equal to or less than the short-range distance, the target is at short range. Short-range attacks suffer no range modifier. Medium-range attacks suffer a -2 penalty to the attack roll. Long-range attacks suffer a -5 penalty. Some weapons have no short range since they must arc a certain distance before reaching their target. These attacks are always made with an attack roll penalty.

While the rule is generally easy to understand there is an edge case that I don't understand:

What if there is no entry for the "short range" category? Does this mean that even at a minimal distance the "medium range" category applies and its modifiers have to be used?

The only weapon(s) with this oddity in the mentioned table 45 of the handbook are staff sling bullets / staff sling stones.

Is the staff sling really so unwieldy that you always attack with atleast a -2 penalty? For me this possible explanation seems a bit off and contrasts with its rate of fire of two attacks per round.

For further context, here are the specific range values for mentioned two missiles – they have the same values:

1. -- (short range)
2. 30-60 (medium range)
3. 90 (long range)

Answer 1

Your answer is contained in the text of the passage you quote:

Some weapons have no short range since they must arc a certain distance before reaching their target. These attacks are always made with an attack roll penalty.

Just as an addendum, it was declared much better in the 1e version:

Weapon  Type                    Damage    Size  Special Information
Staff Sling with Bullet Missile 2d4/2d4+1 4'    Range 0:6:9/No targets closer than 3
Staff Sling with Stone  Missile d8/2d4    4'    Range 0:6:9/No targets closer than 3

Note the size (4' staff), and the range of 0 for short range, and specifically no targets closer than 3 (Which would be 30').