I could be wrong here ( and if I am I' m sure a few of you will be quick to tell me
) but I think the rule is that when you make a substitution, the assistant coach or nominated coach, is allowed on the field for three tackles after the interhange to issue instructions to the team concerning positional changes etc.
Having said that I think it is a farce and I agree that Forshaw was doing much more than passing instructions about positional changes. The rules need amending to stop this abuse.