Hello Roddines,
Thanks for your question, it’s a very good question but I’ll just stop you there for a moment. Manufacturing processes for prototyping and large batch production often differ. Also, while large batch production typically goes unchanged, prototyping processes often change to find the best balance between quality, processing efficiency and cost.
For large batch production, the method stated in the article still applies, but the process for our prototyping service has changed (and we forgot to update this, sorry).
For greater convenience, we now first make the entire plated through hole and then mill them in half. Because copper is a lot harder than the FR4 substrate, the milling bit wears easier and so we need to use high durability milling bits and use a faster drilling speed. This helps produce a clean finish and reduces the chances of sharp burrs being left behind. Regardless, each board goes through a dedicated inspection station for castellated holes where each board (and castellated hole) is inspected and burrs are manually removed.
The result? You can barely tell the difference between the two processes - but more importantly it means there are virtually no restrictions on the board shape since there is no dip plating process.
Hope that addresses your concerns! (and yes, we’ll update the FAQ as soon as possible, thank you for pointing it out)