Of course I would say assessing the performance is relevant, and of course there's a difference between the two types of 1-0 you describe. The point is, that in assessing any performance, you have to carry out the assessment by analysing all the facts as they happened, not as you would like them to have happened.
I absolutely agree with you that you have to take into account all data; and the most important piece of data, when analysing a football match, isn't whether you think you should have won, it's whether you actually did win, or drew or lost.
What concerns me with the statement 'we did enough to win', after a loss, is that any manager who thinks this, risks ignoring the most vital piece of data there is - the outcome of the match. If CW thinks we did enough to win, that suggests he's not looking to improve on what we did. And we need to improve on it, because - and I know I'm repeating myself, here - we lost!