I agree it sometimes seems silly to not disclose information among shoppers, but this is an open internet forum. It is open to anyone. We are not just among shoppers. Not everyone who reads here is a shopper. Not everyone here is even someone who works in MSing. For example, we have had several employees of clients register here to try to find out which company shops their employer. I received a PM from a poster who had registered but never posted. She asked who shopped a company because I had mentioned in a post I did a shop. I explained the ICA and she tried to convince me it didn't matter because of her "special circumstances." Several PMs back and forth and she told me she is an employee of the client.
It's a bad idea to break your ICA. And if someone PMs you, you don't necessarily know who that person is.
But - even if someone wanted to break their ICA and tell you, it would have to be your competition. Subway is shopped by multiple companies. It depends on where you are.