I'd agree that the eponymous first LP is the only truly 'punk' of The Clash's albums but that's precisely why it's my favourite. For me White Riot is pretty much one of the quintessential 70s British punk tracks (far more so than Anarchy in The UK or any of The Sex Pistols' other offerings).
I'm always quite surprised when people knock the first Clash album, it's not exactly flawless but I do think it's by far one of the best albums of that ilk. I know the slightly remixed, slightly different US version is a little less frantic and a touch poorer than the UK version for some reason, but that really doesn't explain the degree to which it get criticised... Oh, I don't know...
I'd would agree that Joe wasn't exactly the most charismatic or overtly passionate of interviewees but I disagree that this somehow makes him disingenuous or not authentic as a punk figure, especially in comparison to Lydon. Yes, Lydon is/was more extraverted and full of 'angry young man' punk rhetoric in interviews, but then I've always found The Pistols as a whole to be a bit of a one trick pony and a more that a little all-mouth-and-no-trousers (after all this is a band constructed by McLaren with their image as the primary concern). For all his punk posturing and insipid social commentary Lydon's actual politics have always been somewhat lacking (this is of course a 53 year old man still flogging his punk credentials whist shilling butter for a living...)
Personally I think in both musical and political terms 'The Clash' is an archetypal British punk album, and surely punk album = punk band regardless of whatever style of band they might later transform into?