Back when release artifacts were hand crafted, these often contained leftovers that weren't meant to be shipped, like cut content [1] or debugging symbols [2]. When I stumbled upon debugging symbols hidden inside the data archive of the demo version of the video game I'm reverse-engineering, it was an unexpected but very helpful surprise.
Nowadays with CICD, automated builds and other modern development practices it probably happens less often.
CICD pipelines can also work the opposite direction. No one looks into several thousands of console output unless there is some error. Also the tests are likely to pass even with excessive content in the final release package.
So my intuition is rather opposite. It may happen more often. Or at least CICD makes it more likely to happen than manual building. There might be other factors too.
I'd say manual building has a chance of a slip-up every time it is done, whereas automated building has a chance that it will slip-up every time it is executed.
Nowadays with CICD, automated builds and other modern development practices it probably happens less often.
[1] https://tcrf.net
[2] https://www.retroreversing.com/games/symbols