Hotfix 5 August 2022:
Soul Leech grants an absorb shield based on 12% of damage dealt in PvP combat (was 8%).
It still shows 8%.
Hotfixes in many cases are not able to change tooltips on abilities, as said tooltips (in all their localized versions) are actually stored locally in the files of the game installation (meaning, it’d usually need a client-side patch to alter the displayed information). This is likely a case of exactly that. 