GIS is basically "serious mapping software", and when it's used for city planning or other large GIS-relevant activities, accuracy and precision are non-negotiable requirements.

IOW, your city might be using QGIS to plan the city and verify everything being done on it, down to cm level accuracy. So, any subtle bug is a big deal for these kinds of software packages.

While doing construction work (regardless of infrastructure or buildings), the plans are laid and verified to that level. The haphazard spray paints on the ground are indeed big deal, and has a digital copy in the GIS software.

It's not only used by municipalities and/or governments either. Research teams use GIS packages extensively as well. I briefly worked with a research team working at Antartica. These GIS software and related ecosystem is their both bread and butter and foundation to anything they do.

A patch generated by an AI model breaking these software packages have cascading and important effects. So, the software needs to stay dependable and reliable.

Data portal for South Korean team: https://kpdc.kopri.re.kr/

They're not the team I was working with, though.