VAT excludes the VAT paid when the company purchased the raw materials, i.e. it's paid net.

The end result is, the consumer pays VAT which is 20% of the price (i.e. 20% of the revenue), and the tax is spread out evenly across the whole production supply chain, weighted by the amount of added value by each company in the chain.

I'm not sure what you mean. If you assume all sales were to consumers it's true that the government receives ~~18% of Apple's revenue compared to if Apple sold nothing. Or are you just referring to the small difference between counting "revenue" as inclusive of VAT or exclusive of VAT?