WebGPU not yet a W3C standard (it's at the previous step, as a "candidate recommendation"). Apple's WebGPU implementation went live
before Firefox's implementation.
WebRTC went live in Safari the same year that the non-draft version went live in Chrome (Chrome supported the pre-standard webkit-prefixed version for some years before).
Similarly, Safari added support for WASM the same year that WASM was standardised (once again, Chrome supported a pre-standard version ahead of standardisation).