You're quite correct, HawksNut. I just investigated and the RMSS/FRP data file mistakenly used the same internal identifier for Spear and Javelin. I have corrected the data file. Please re-install the tables and choose/save Spear again to fix.
Note that this only affects the RMSS/FRP data file. The RM2/Classic data file uses completely different identifiers and I have checked to ensure the Spear and Javelin are unique.
Thanks for spotting this, HawksNut. Cheers.