From reading the extensions description, this seems like exactly what it’s meant for. Means extensions for Atom, VSCode, etc. can be created per language (Python, Go, PHP, Ruby, etc.) which can contain all the tools needed for full language/IDE support (library, linter, etc.). I’m assuming a Flatpak extensions is easily distributed on Flathub and conveniently displayed in the GNOME Software app as add-ons to the main application. That makes it user friendly to extend your favorite editor with support for the required languages so the Atom/VSCode in-application extensions work too. Even makes it easy to scope extensions for major language versions (Python 2/3, PHP 5/7, etc.).
Anything with a wrapper requiring users to alter the language commands inside their editor to flatpak-spawn, or building all kinds of podman containers, or using fedora-toolbox is simply not user friendly. If we wanted to tinker with everything, we would probably all be using Gentoo. I know the solution is upstream in Flatpak/Flathub, but i.m.h.o. Fedora needs that to be a “it just works” solution.