I hate some of these answers from IFAB. Every Lw exam I’ve ever seen would say that this has to be a caution as there is no offense other than USB. Yet IFAB says it is an IFK and maybe a caution. OK, but if they are going to say it’s an IFK, it sure would be nice if they would give a reason from the Laws instead of just giving a conclusory answer like this. (Or, perhaps this is one of those questions that will get revised.)