The point of XG isn't to tell a story or narrative,. it's literally just applying mathematical probability to football chances based on a number of criteria.
As such, it's not the job of XG compilers to make calculations based on what might have happened (ie the first chance scores) but on what actually does happen. And you can call this "a flaw" but it isn't, it's just a mathematical representation of what actually happened - and it's up to anyone using XG to contextualise it. Every subsequent event could/would be potentially be effected by what might have happened in a previous event.