Mostly unfounded in my opinion. They took the _exact_ same strategy that go did when they moved from C Go to a Go based compiler.

First they essentially wrote a translator that preserved the C idioms (so it wasn't idiomatic go) until they had byte for byte output.

Then they started changing code one by one to be more Go-based.

Bun is doing the same. Right now it is mostly a one for one translation of the zig code. Over time they'll make it more idiomatic Rust.