Showing my age here. A family member of mine used to run a local theater. The booth had multiple projectors, because films came on multiple reels (and once you knew what to look for, you could not unsee the reel switch indicators). So we've had the technology for a long time to pause a feature before the credits and roll another featureette and then switch back.

That’s actually a big no-no in cinema. You don’t just splice a movie you’re showing to insert stuff, much like museums don’t usually draw on their paintings. Showing the work as the creator intended is the whole point.

yes we do but that's disrespectful to the movie (and to the people who made it)

And slapping a featurette in front that spoils the whole plot isn't?

In most cases the credits are not integral to the artistic vision of the movie. Most people get up and leave when the credits start.

"slapping a featurette in front that spoils the whole plot isn't", uh it is disrespectful, that's why I wrote the piece

I'm well aware that people leave during the credits.