no, you all have it wrong, it is not a nice person or a generous person.
it means someone who claims they would give you a million pounds - if only they had it.
e.g, - if i ever win the lottery, i will give everyone on AB 3,000 pound each... how generous am i? don't you just love me? aren't i kind and generous?
chances of it ever happening are so slim, i need never worry about having to stick to my word - it is easy for me to be so generous here...
if they had 2 million, they promise sincerely that they would give you 1 million of it - never going to happen though is it? - so its very very easy to say and sound generous
someone who is so generous in theory - in order to seem nice - because they know they will never actually have to give you anything