Picture a fork... Old rules on one side. New rules on the other.

You’ve updated for smaller OP_RETURNs.
Someone sends you coins born from the other chain.
You smile. You check.
Your node shrugs and throws it in the trash.
They scream, I paid you! You answer, calm as stone: Not on my chain, you didn’t.

That’s it. That’s power.
Not bluster. Not hash rate.
Math...