I don't think PRONE status has been working in BG3 as it has in RAW since several patches. When an enemy is PRONE in BG3, we do not have disadvantage when attacking from range nor advantage on melee attacks.
Additionally, PRONE no longer auto-fails DEX saving throws so Sacred Flame is no longer 100% success on PRONE enemies. This should be addressed by Larian because I'm sick of them changing stuff.