It’s a small distinction, but actually if the band showed up and found all the brown M&Ms still there the plan would have already been a failure.
The reason it was in the contract was to make sure the promoter had read the contract before signing it and understood what they were getting into.
Band riders are almost invariably redlined. Bands ask for all sorts of crazy shit and you cross out stuff you can’t provide or give a substitute brand name (like if the venue has an exclusive vendor relationship with Coke instead of Pepsi stuff like that) and then you work out any kinks and finalize it.
The reason to put the M&M clause in there is to get the promoter to strike the clause during the contracting process because any competent promoter will read every line carefully and strike something like that.
So when they do you know they read it and know what they are doing are comfortable signing a deal with them.
You would never want to be arriving at the venue with the clause still in force, that’s a sign you have a larger problem.
Source: I was a concert promoter in the 90’s