Because if you're a small distiller (ie 1800 litre batches) you need court certification. If you're big (1819L+), you don't. My reading is that 1800L is the minimum size and there's an extra hoop to jump through if you're going to be that small.
The most depressing thing about this, I think, is the way they expect you to fully scope out, spec and draw up the plans for your premises and system, and then they tell you not to buy any of it until you have approval. I imagine lots of phone calls to vendors saying "Sorry, not heard from the Revenue yet", followed by things being sold out from under you, followed by having to start the whole application process again <!-- s:x --><img src="{SMILIES_PATH}/icon_mad.gif" alt="

" title="Mad" /><!-- s:x --> It must be nearly impossible to start a commercial distillery other than as an add-on to an existing business where you already have room to spare for it. I certainly don't envy the Porterhouse with their project.