In my experience, even if the company has a platform team, they still expect senior/staff software engineers to know about platform/infra topics and work on them. It’s strange because those very same companies don’t expect platform engineers to know about product related topics.

For example, while a software engineer needs to know about let’s say, DDD, the business logic of the product, and K8s, a platform engineer in the same company only needs to know about K8s.

Knowing about something doesn't mean it should be bogging down half your workday though. I think it's important for engineers to understand a high level the platform that runs their code and how it scales, but if they're spending a large chunk of their time orchestrating deployments and screwing around in IAM as OP insinuates, that's a red flag IMO. My teams certainly don't.