If the majority of the code and functionality is written by WordPress, Having a little GPL component in there will not affect them to change the license. GPL's idea of infecting copyright with small libraries is a convention. I don't think it will hold in an actual court that will test who wrote what at what degree of substance.

Did the little GPL component force itself into the codebase without anyone noticing? Was it so useless that nobody could have removed it from the project to get rid of this obvious parasite?

I think it will hold in court specifically because, since it is so aggressive in what it is set to do, a company choosing to use it in their otherwise non-GPL codebase is declaring that it is not easily replaceable and thus proving it contributes to the overall value.