This is an anecdote - plenty of firms are using Scala in their data engineering stacks and it's a great tool for the job.
While maybe not strictly necessary per se, it's a great way to get a foot in the door, and provides a great way to foster advanced type systems and functional programming (I personally find it to be a really fun language to write in to boot).
Regardless of the source I think the main point folks are missing is that a lot of DE jobs will require you to know Scala so it's a good tool to have if you want to be a DE somewhere.
SQL is also an amazing tool and you should definitely learn if but there are a lot of DE jobs out there with Scala in the "Requirements" section of the job listing. Parts of the industry might be moving away from it, but if you're looking to make a jump into DE I think you're hamstringing yourself by avoiding Scala.
Scala, when it's not used because it's just what someone learned the ropes with, is the Haskell of data science and machine learning: it's what people use when they want to inflate their credentials and/or egos.
sql, python, terraform, maybe some basic java. Airflow is pretty common. Whatever the company is migrating away from. As long as you`re good at one of those and can pick up the rest on the fly you should be fine to start out.