I agree, but that's exactly the point. This article is referencing more up to date data that implies that the previous predictions were wrong.

Aside from the stock market they're not referencing any data.

...Wow this article is actually a load of crap.

They say "... now economists also believe the impact of the vote will be relatively modest, compared with some early fears." but if you click on the link they provide to back up that statement it's another article from before the referendum and it doesn't talk about post-referendum Britain but it tries to explain a Q2 slowdown with the uncertainty from the referendum. And now that we know Q2 growth wasn't bad they're saying "Brexit didn't affect us as much as we expected!" which is true but it's about the first half of the year not July or the future.

Aside from that I too think predictions made today will be "rosier" than predictions from a month ago but that is probably because a month ago we thought article 50 will be triggered soon. Now we know that won't happen for another year.