WasmGC is a feature you can opt in to, rather than a core feature of the platform. It's more of an enabler for languages that expect a GC from their host platform (for things like Dart and Kotlin). Inversely, other forms of bytecode might have linear memory, but the JVM isn't one of those.

For the purposes of OP's question, the memory model difference is one of the key reasons why you might want to use wasm instead of a java applet.