Please don't answer me 'in two weeks'... ;-)
Well half a month then 
Seriously, if someone can see the future there is much more than 'accurate estimation' one can do.
I am sure, if you can accurately predict the date at which the chips will arrive and the broads will be printed and populated with all the required components (received in time or when they are), Punin will be able to give accurate estimation, but for the future there are just rough expectations ... there are no reasons for delays right now, but this doesn't mean that he lied if there are some latter.
Producing 5 or 10 boards is not like producing 1-10k especially if you don't know is it 1k or 10k
The difference between a company A and a company B in mining hardware will not be just the GH they can deliver... but when they can deliver and how accurate are these estimations.