What is the actual benefit of restarting a container when updating its configuration instead of updating the configuration at runtime (e.g. Spring Boot supports listening to ConfigMap changes or Spring Cloud Config Server has this feature)? I can actually see none and I can see some drawbacks such as a need to reset TCP connections.
Unlike Spring Boot, other stacks such as Node.js, Go or Rust actually don't have as big overhead when booting up. The problem with Spring Boot is that it just takes longer than any other "modern" stacks to start up because it's booting up JVM and Tomcat. Those two technologies were here well before Docker and Kubernetes were a thing and honestly, that's the price to pay to run Spring Boot in containers.
And what's the benefit? If you're a single developer, probably none. If you work in a team and everybody tinkers with live ConfigMaps and environment variables, it can get hairy really quickly.
Assuming you're using for example Terraform to manage your configurations then everybody gets a nice overview of what is going on and which values are injected where.