I'm well aware it's there, but if the rules need to be referred to in play then then IMHO that's poor design. One of the goals of 4th was to reduce the number of rules that only come up rarely.
While immediate actions don't come up rarely the fact you cannot use them during your turn only comes up on three occasions. These three items.
Until these items the only immediate reactions were triggered by events caused by an opponent thus HAD to happen in an opponents turn. Hence you didn't need to know they couldn't be used in your turn.
The trigger for these three items can come up in your turn (in fact is more likely to) so in order to understand how these items are used you need to know that immediate reactions cannot be used in your turn. These are the only three occasions this rule comes into play hence the rule is obscure.
It needs to be fixed because it the rule only ever comes into play with these items. A rule in the core book that is only used by three items in the whole of the game is a bad rule. That or the items need to have that rule in their text, because people are going to forget a rule that comes up so rarely.