The link explains that AdBlue will be ” refilled by the dealer as part of your vehicle’s standard service”
The following makes it quite clear that you are expected to buy AdBlue at any other time that it is required –
“If you cover more miles, you may find that you need to refill the AdBlue tank more regularly.
If the warning light appears, you can top up the tank using AdBlue fluid which is widely available to purchase at petrol stations and motoring stores.
Always remember you can contact your dealer for advice on refilling AdBlue if you’re at all unsure.”
The article was written in May 2018, so anyone getting free AdBlue outside of standard servicing for the last few years was lucky.