Please quote me a rule that enables any Wizard to cast Cleric spells (emphasis on "any", so not including multiclassing into Cleric or taking a specific feat).
Well played ... but you forget something.
https://dnd4.fandom.com/wiki/Rule_0Rule 0 or rule zero in tabletop role-playing gaming is the unwritten but commonly understood rule that the game master can override published game rules for any reason.
There. :P
Rule, that enables any Wizard to cast Cleric spells ... if GM (Larian) say so. :P
Just for the record i dont disagree with you ... i never use Cleric spells on my Wizard ... but still i dont see any reason for Larian to bother with this honestly.

People who wants that will mod it imediately ...
And people who dont, will never use it ...