You might want to re-examine that claim. On a full cargo hold, perhaps?
The cargo hold also acts like a secondary fuel tank if you choose.. Jeez
So yes, on a deep space build you should have 26780 tonnes of fuel minimum, unless you are taking a shipyard for others, then you should at least expect your passengers to carry fuel to offset the 3000 tonne shipyard you have bought for them. It needs to be planned correctly.
Now obviously things are worse for those that want to provide services for others in the black,and have high mass carriers.