This is moot and going nowhere.
121 can be either way S12E1 or S1E21.
You’ve never seen %d%d format?
The real-life example existed. It failed to parse as the user wanted and , given both episode numbers were valid, no automaton in the world could know the intent.
I write FSM’s in my job. There are insufficient delimiting characters in a 3 digit sequence to parse a season and an episode.
Closing.
