The statement reproduced from the advisory website about EU VAT clearly indicated that VAT must be paid prior to removal from customs, for goods imported from outside EU. This does not apply to goods imported within EU, which can be considered for a suspensive arrangement.
So, logically, the importer pays the VAT, at the rate of the receiving country, prior to removal from customs, for goods imported from outside EU.
Now the importer is out of pocket until the goods are sold on.
No, he will reclaim the VAT paid on his next VAT return, whether he's already sold the goods on or not, so he might be out of pocket to that amount for up to about 3 months. But during that time, he will also be collecting VAT on his sales which is to be passed on to Customs & Excise on that next return, so he will have the benefit of that money to balance it out.
To further illustrate the example, suppose Brico Depot (a DIY shed operating in EU) import tools from UK (following a Brexit), they would have to pay VAT prior to removal from customs, but they couldn't reclaim that VAT until goods are sold to the end user, perhaps many months, even years, later.
You don't seem to understand how the system works, so I have to ask if you've ever been VAT registered for business?
Take a case where you're running a business and not importing, just buying from another U.K. business. You buy a widget from your wholesaler for £100 and you pay him £100 + 20% VAT. You put that £20 down in your VAT accounts as being tax you can reclaim on your next VAT return. Now you sell that widget to somebody else for £150, and add 20% VAT for a total of £180. You put the £30 VAT you collected from your buyer in your accounts as being due to H. M. Govt. Net result as far as this one widget is concerned - You now owe H.M. Govt. £10.
It doesn't matter whether it takes you a week or a year to sell the widget; as soon as you've bought it and paid out the VAT on that purchase, you can reclaim the £20 VAT you paid on your next return. When you sell it, you are liable to collect the £30 VAT on the sale price and will declare that for payment to H.M. Govt. in whatever happens to be your next VAT return following the sale. That may or may not be the same return as the purchase of the widget.
The person to whom you sold the widget repeats the process in the same way, reclaiming the VAT he paid you, and passing on the VAT he charged to his buyer. The net tax collected at each step along the chain is based on the value which has been added to the item, hence
Value Added Tax. As far as a VAT-registered business is concerned, it never actually has to pay VAT on the widgets it sells, because any VAT paid for their purchase is reclaimed. It's only when the chain reaches somebody who is not VAT registered - be that the end domestic consumer or a small, non-VAT registered business - that the process or paying and reclaiming VAT stops.
Now if you decide to bypass your U.K. wholesaler and import (from outside the EU) directly, the only thing that changes on those arriving shipments is that instead of paying VAT to your British wholesaler from him to pass it on to H. M. Govt., you get charged directly on the arriving goods.
You can still reclaim the VAT paid on your next VAT return, just as if you'd purchased from a U.K. business.