I think the extent of change in build week could depend on what the change(s) is (are) that you’re making and whether or not your build week had already been confirmed. If you had a confirmed build week, then changes can’t be made to the car’s spec, so any change would effectively be treated as a new order which would mean moving to the back of the queue in terms of build / lead time.
Where a build week hasn’t been confirmed, I’d expect simple changes like changing the car’s paint colour to have less of an impact on build week than more extensive changes like adding multiple options, where there’s a dependency on the third party companies used by VW to manufacture the options, but that’s just supposition on my part. In the case of alloys, VW don’t manufacture their own alloys - they use companies such as BBS, Ronal or Borbet, so if those companies have any issues getting raw materials needed for the manufacturing process or there are Covid impacts on their workforces, then there‘s likely to be knock on impacts to vehicle production by VW and other vehicle manufacturers they supply wheels to.
I’ve just read over on golfgtiforum.co.uk of a a forum member with build week 47 (2021) who changed their paint colour. Build week of their car moved to week 18 next year, so added around five months to the lead time.