No, see you’ve fallen into the exact trap I just described. The “exact same binaries” is not true. The Steam build will have the Steam overlay SDK integrated into it. The GOG build won’t. Each store may require its own SDK and API integrated into the build. But even they were the exact same binaries, you’ve still got to think about QA, build pipelines, storefront configuration (including achievements and online subsystems like leaderboards, parties/lobbies and voice chat, plus collectables and any other bespoke stuff a particular store has) and community management, plus any age ratings and certification/testing each store requires (though PC is usually pretty sparse on this front).

For small indie teams, all of this can seriously eat away at your time, so it makes sense to limit how many stores you target based on risk vs reward.

Edit: btw I’m not trying to be a troll, I just know from first-hand experience. I’ve been in the games industry for over two decades and have done everything from AAA to running my own indie studio. Indie development is brutal, you really have to be clever about your time management otherwise your risk of failure skyrockets.