I did not know if upgrading this tier 4 weapon a lot eventually makes it better than an upgraded tier 5 weapon. The in-game text is not clear on this. According to the fandom page, it appears the answer is no- https://pixeldungeon.fandom.com/wiki/Shattered_Pixel_Dungeon/Weapons#Runic_blade

Given that, I would like to know the reasoning behind this game design decision. Is this weapon supposed to incentivize players to wait until tier 4 weapons to start upgrading weapons with scroll of upgrade? Or is this weapon supposed to incentivize players to upgrade runic blade instead of upgrading a tier 5 weapon? The latter seems to not be the case, since tier 5 weapons with the same amount of upgrade seems to be stronger than the runic blade. However, the former may not be the case either, because if the beginner player does not know to wait on using scrolls of upgrade until they get high tier weapons or armor (instead of throwing them all into worn shortsword like I did originally), then the beginner probably does not know that this weapon exists either. So what is the game design decision regarding the effect of this weapon?

Thank you for your help.