Imo I think observing a crime like that but not reporting it (so more crimes can be amassed by that person) should be considered legal endorsement of the activity. You were aware of the infraction and chose not to report it or otherwise act on. That you were hoping to “bank” more crime from the criminal seems irrelevant to me - you chose not to pursue legal action even after clearly being aware of the infraction, which tells me you chose inaction.

But of course bringing our laws in line with morality and reason would require an enormous overhaul of the system, so instead we have this bullshit.