Yes, bundling is allowed only for sources. You can package all dependencies in source form into a single vendored tarball.
OP never talked about bundling blobs, only you. Also OP never talked about vscode.
Flathub != Fedora. All Fedora packages must be built from sources (except firmware).
Indeed, and they are built from sources on Flathub and that exactly the point. We can do the same for Fedora.
Keep mislead people and twisting things if this helps you with packaging electron apps on Fedora.