I've had one argue that as it would in effect although not actually raise my CHA to 20 it would give me more bonus spells from the bonus spells from ability scores list due to CHA 20 as spells are a sorcerer class ability and the + 2 CHA would not make my CHA 20 but make it act as 20 for bonus spells ECT.
also as you have said some argued that skills should be +1 well only the CHA based ones if they were class skills that is.
another disputed this.
also they could not be sure as they said i sort of already get this from fire affinity racial and they was not sure taht it could stack.
which if it cannot stack then it makes the boon pointless for a Ifrit sorcerer unless i am miss understanding something.
sorry if my grammern and spelling are not to great also :)