Fighting games are so full of funny assumptions and legacy street fighter 2 engine quirks that fighting game people take completely for granted and have no idea how to explain (or even forget that it needs explaining)... even to someone who has intimate knowledge of other game genres some of this stuff is totally counter intuitive.
The biggest thing that comes to mind is the input buffer and the fact that motion inputs are completely independent of character animations. Motion inputs like ⬇️↘️➡️🅰️ work the way they do because the game is silently keeping a history of your most recent inputs, and what move comes out of your character is based not just on the state of your character or anything else reflected on the actual screen, but also the story told by your input history. This is why you can do a ⬇️↘️➡️🅰️ fireball as part of a combo, or ➡️⬇️↘️🅰️ reversal DP on wakeup, despite your character appearing to be completely locked into an animation...