If "bench" equals "maximum carrying capacity", IIRC that would be 100 pounds for a Str 10 character. 200 for Str 15, 400 for Str 20. Also, you've listed the upper bound rather than the lower.
Furthermore, hunting bows had a lower draw weight and DnD doesn't seem to distinguish between an "English" longbow and a hunting bow (though I suppose it might be represented by a shortbow).
The "longbow" is as much an "english longbow" as a longsword is a "german longsword". In Afrika and South America people are using bows that are as long as the user is tall, which would also fall into the weapon type "longbow", while I think a "shortbow" would be 3/4 of that length and shorter.
We are not standing on the shoulders of giants, but on very tall tower of other dwarves.