A-pillar broken is rarely seen in car crash test. Such issue should be caused by the following reasons:
- Poor design, e.g. the front structure is not optimized for impact force absorb. It's a German-brand car. German are too proud to let others, especially if it is a country in their eyes is with an inferior auto industry, to interfere the German-brand car design. It's not difficult to imagine it.
- Using downgraded materials purposely. E.g. a harder steel grade should be chosen for the safety consideration, but the car company chooses the lower grade for cost control. Should not be surprised here considering VW needs to pay the diesel-gate scandal fine in US. A big amount of money, hence it wants to secure higher profits from its China business. Also the lack of side air curtain of Passat could be seen as another proof here.
- Using an unqualified supplier that fails to meet the quality standard. I cannot exclude the possibility here fully, to be very honest, because I don't know who exactly supplies the steel of the BIW (body-in-white) to SAIC-Volkswagen. However, considering A-pillar is the most important part to vehicle safety, steel for making A-pillar could only be sourced from super large & credible steel companies. And such steel companies usually serve a variety of different car OEMs. But A-pillar broken is TOO rare to see in crash test. Therefore I don't think it is the supplier's fault
- OEM's own mistake in manufacturing. SAIC-VW's past quality record is not bad. It's not the top-class in the industry, but acceptable. See the survey from JD Power. SAIC-VW's PP100 (problem per 100 cars) is 111, better than the industry average (116). So I don't think SAIC-VW's workers should be blamed for A-pillar broken, considering the "rareness" of A-pillar broken.
https://china.jdpower.com/zh-hans/press-release/2019-china-vds-cn
Short summary: the Passat's A-pillar broken issue is more likely to be caused by poor design, or using a downgraded materials purposely. It's Volkswagen's responsibility, because sourcing and R&D is under its full control.