Presumably, you have written a carry out, before, or check rule for examining the table. Since such rules don’t end the processing of the action, other applicable rules for examining things will also fire (in this case the examine supporters rule).
Inform really expects you to put particular cases like these in instead rules, which will stop the action after they have run.
If you’re worried about Inform’s book-keeping concerning the success and failure of rules and what actions have been performed, add the phrase ‘rule succeeds’ to (the end of) the instead rule.
Tip: The debugging command “RULES” lets you see what rules are processed for the commands you enter. The one immediately before a normal response from the game is the responsible rule. (RULES OFF to turn it off…) Then you can look that rule up in the Standard Rules, if you want to take a close look at what it does and when.
Actually, I’d agree with you if this is just a one off case with any other supporters following the examine supporters rule and there are no extra examining rules in addition to the standard ones.
However, authors may sometimes add additional examining rules, which should be firing. A instead rule would stop this. Also, adding instead rules could easily encourage the overuse of the instead rulebook. In fact, I’ve even seen instead rules which literally replicate the the carry out and report rulebooks.