Not really the ethos of C(++), though of course this particular bug would be easily caught by running a debug build (even 20 years ago). However, this being a game "true" debug builds were probably too slow to be usable. That was at least my experience doing gamedev in that timeframe. Then again code holding up for 20 years in that line of biz is more than sufficient anyway :)
When I was doing gamedev about 5 years ago, we were still debugging with optimisation on. You get a class of bugs just from running in lower frame rates that don't happen in release.
