CHANGELOG から，GC と extended-const に当たりをつけて試していたら GC と一緒に何かの feature (まだ不明) が有効になっている時にだけ起こることがわかりました．
$ wasm-opt -Oz -all hoge.wasm -o hoge_host_opt.wasm && wasmtime hoge_host_opt.wasm warning: active memory segments have overlap, which prevents some optimizations. Error: failed to parse WebAssembly module Caused by: heap types not supported without the gc feature (at offset 0x2e8) $ wasm-opt -Oz -all --disable-gc --disable-reference-types hoge.wasm -o hoge_host_opt.wasm && wasmtime hoge_host_opt.wasm warning: active memory segments have overlap, which prevents some optimizations. Hello, world! $ wasm-opt -Oz --enable-gc --enable-reference-types hoge.wasm -o hoge_host_opt.wasm && wasmtime hoge_host_opt.wasm warning: active memory segments have overlap, which prevents some optimizations. Hello, world! (edited)