What's the point in having a menu in the first place if people can just order what they like?
If you don't like their menu don't go.
Because a menu won't suit all no matter what. It's adding to it, not asking for a custom meal after all. You will lose a lot of customers with that mind set.
It's easy to see why the restaurant did it, they think just like you. We are people man, no harm in helping people out. A good manager can make good choices on a case by case basis imo
You are right, I wouldn't be going to your place or a few others if we egg/piece of ham added to our food the way we would enjoy it more.
It's also very common for different cultures to enjoy food in a different way. No reason in denying them what they like cause a restaurant wants to be "tough" and tidy on a menu. If this was my restaurant, why not just be kind to people's likes?
Rules are fine and usually for those who can't make the best choices but rules are somewhat of a guide for a manager not always concrete. He made the wrong choice imo and the customers should be appreciated and the workers as well honestly. It isn't about how much time he has spent there, it's not that hard to add egg or any other single items such as cheese.
I can imagine if a customer asked for the nacho sauce to be poured on his burger you would also say, can't man, rules!
Give him the price of the nachos, dump it on. Give him the chips and tell him the price. Tell him your fine to add it on but you have to add the cost of nachos. Tell him it's the best compromise you can do for the system but your more than glad to get the cheese on his burger. If he isn' t happy with that ok. That's all but you tried. Even though, no chips and a slightly cheaper price may can be done by some no reason in making it complicated. This is why you have managers that can make good calls to begin with.
Of course if you stick to this thinking, your cooks stick to it and you only have (we only make items this way mentality) then you will run into problems. You have to train your peropld to handle situations as well so if you and the place are in this mind set then it's not going to work. If the manager is a people person, has a system in place so the cooks know that someone may add or take something off then it won't be a problem for the cooks, customers or waiters. A much better experience for all involved.