A couple of definitions:
NGC - Brilliant Uncirculated - an adjectival grade which NGC defines as being MS 60 or higher
Royal Mint - Brilliant Uncirculated coins are struck to a superior standard than their circulating counterparts.
Your first link has nothing to do with minting process. The second link justifies a year line for BU:
Varieties are determined by:
- Specific strike processes (polished dies, proof strikes…)
And this in the Numista guidelines for year line comments:
Record further details specific to individual lines in the comments field:
- type of strike, for example proof, specimen, polished dies, matte, etc. Do not record regular strikes in the comments.
Regardless, in the Numista catalog, year lines are routinely added for BU coins.