Such bugs are definitely still possible if you’re writing for modern systems in a similar style (large blocks of contiguous memory interpreted only as needed).

Just yesterday I was storing my color planes in three separate adjacent buffers for reasons, and if you looped the player off the bottom of the screen it came back up in a different color on the top. Now I need to figure out what to do with that…

That's quite different from an actual, playable level appearing out of a bug.

Not really - if I had any tilemap structures for the level yet, it would've had a similar effect.

The point is this stuff arises whenever you have, like `char level_data[8][4][10][100]` rather than, like `class level { std::vector<actor*> actors; std::vector<sprite*> background; }`. And storing stuff in large contiguous blocks that can be interesting when misinterpreted is still a pretty good way to write modern games if you don't have OO brain rot.

Sorry, I missed the part where you mentioned that you were writing your game in a similar style to classic games. Of course that does open up the door to similar bugs causing similar results.