Why "no?"
Reason above. But it is simple, the spear is a good weapon (which of course the battle fork is as well, but hell, the spear could be much better and more annoying) with 4 side attacks. Thats more than just 2 (up and down, which can be blocked by most ppl, unless spammed). People should decide what items they take with them with 4 slots available.
For example if you take a spear with you, which currently takes 2 slots and the Huscarl shield which also takes 2 slots, you cover all 4 slots and cant take more with you. If the spear would only take 1 slot, you could take additional war darts, another 1 handed weapon or whatever you like... Imo there should be some restriction for builds that needs more than just their simple 2handed weapon (or polearm). I mean, if the spear gets an exception, which is the next item where people asked for? There are similar weapons like the spear which also have 2 slots needed.
In my opinion, the shortened spear is short enough (thats why the name...) to be used for 1 slot, the spear is longer and deals more damage, hence more space is needed. Actually due to realism it couldn't even be taken with into battle that easy while using another weapon at the same time... unless you do not sheath it (thats also why lances and pikes drop, in Vikingr any spear or 2handed Weapon drops when put away).
The only difference between the 2 weapons youve shown, are the slots and the advantage of the spear with 4 attack directions. Now the question is, would you give up the 4 attack directions for 1 slot? If yes, the 2 weapons would be equal, but every weapon should be different if possible. =)