No, you're missing the point. We have conclusively "linked changes in climate to climate change" as your comment eloquently put it. That's not really up for debate. But weather systems are extremely complex and extreme events have always occurred. So you can't say that this one specific heatwave is caused only because of this trend.
When it comes to the urgency of doing something about it, that doesn't matter. It's absolutely sufficient to say "this type of event will occur increasingly often" to establish that it is an existential crisis. You don't have to be able to prove anything at all about this one very hot week in order to say that it is probably the single most important issue for us to tackle (along with the politics that prevent us from doing that).
But we don't have the science and statistics to generally link individual events to a trend in isolation, and we shouldn't misrepresent the science that way.
Scientists do actually make attempts to investigate the contribution of the trends to specific events, it's called extreme event attribution, but it is a very young field and the error bars on everything are still huge. That said,
But the quote from the article was strictly correct in saying "it's hard".