When the VAG Indie that we used replaced the cam belt on my wife's 2002 Polo with the BBY engine, they always added in an extra small top idler as it does fail and is not included in the normal kits, or was not back in 2006 and 2010!
The extra cost of a genuine belt kit can sometimes to due to VW Group having modified some parts, buying aftermarket, including Gates might not end up with latest version of equivalent parts, you pay your money and -------- .