So it seems like they have been spot on? TFA quotes the OBR as estimating a 4% negative impact and the CEFR estimate of -5.5% cumulative impact.
https://news.ycombinator.com/item?id=48473246
The actual data doesn't support any of these estimates.
Note the response of the guy I was arguing with. Faced with the reality that the sources he/she trusted are lying, they rejected the honest source they asked for because of "bias". This kind of motivated reasoning is everywhere in this debate. Quite annoying.