Given that
a) spears come in different sizes,
b) their users come in different sizes, and
c) everybody is aware of both a) and b),
then both the dwarves and the players should know that not all users are going to be able to handle all spears equally well. A short and scrawny dwarf might need both hands to use the exact same weapon that a tall human confidently handles with one. There were broad-bladed spears, designed to inflict a larger wound on an unarmored target. There were armor-piercing spears, boar-spears, fishing spears, and javelins. The Romans used the pilum, a javelin with a sharp steel head but a weak iron shank that bent upon impact--making the weapon useless for throwing back at the Romans. Mounted humans might use lances. Pikes could be a multi-tile weapon, giving them a unique property. There is a vast wealth of potential diversity, and I for one would hate to see it all vanish under the one word, "spear".
Similarly, the staff has multiple variants--the Chinese alone have 3 principal sizes of staff, each in a certain proportion to the height of the user. Again, a dwarf and a human would have different definitions, and different uses, for the exact same weapon. Who's to say where a baton becomes a cane becomes a quarterstaff becomes a long staff? It's all relative. Placeholders are all right for now, but as I said, I'm for variation.