The distinction that finally made this make sense to me: there is a ruined pan and there is a ruined dinner, and the rule conflates them.
A ruined dinner is what most people actually experience. Iron dissolves into the food, and the food tastes metallic and sometimes goes an unappealing grey-brown. It is unpleasant and it is over, the pan is fine after a re-season. That is the outcome the rule is really protecting against, and it is a dinner-scale problem, not an equipment-scale one.
A genuinely ruined pan takes sustained abuse and is quite hard to achieve. Pitting from long-term neglect and rust does far more damage than any tomato sauce.
So the honest version of the advice: acid takes seasoning off faster than anything else you will cook, and seasoning is easy to put back. Know it is happening, keep the contact time short, do not store food in the pan, and re-season when the surface starts looking dull rather than dark.
One last practical note since you have a well-used pan: the more you cook fatty things in it, the more resilient it becomes to this. The pans that survive acidic cooking are the ones that get used constantly for everything else. Regular use is the actual maintenance.