.............. there's actually a very easy cure for this if IHG chose to.
They could simply use the magic words "promotion" when they have an offer they want viewed as restricted. Without it, most customers are unable to differentiate because the word "promotion" is vague and means different things to different people.
For example this year I've stayed at IC VIE when there was a "special promotion" of a free glass of Sekt and free breakfasts. There was a sad one with free broadband. Quite a few others really. There was a special "Insider Culture" promotion. Arguably these rates became "promotions". But all of them you could use BOGOFs if you chose.
I think they should just make clear in a way that is clear to the majority what you can expect or not.