Most of their products are like that. There are a lot of specific language support features in each one that may become available as plugins later on but not at the same pace or “fullness” as the specific product itself.

For example, PHPStorm has good JavaScript support but if you want really good Typescript support you should probably go with Webstorm.

Alternatively, I can totally write Rust code in Webstorm through the Rust plugin but I’m better off using CLion that has better support (or now RustRover which will be where all the latest Rust support features are added, although it’s still a preview product afaik).

Also worth noting though that there are indeed some “tiers”. Like Webstorm won’t support PHP but PHPStorm will support JavaScript/Typescript (again, not fully but enough to maintain a front end operating off your PHP backend)