Well the examples don't always follow the rules then. Cold Iron is clearly a +4 catch. It's easily acquired and anyone who knows anything about magic knows about faeries and cold iron. For many of the little faeries it makes sense to be only +1 or +3 because you can't have a catch that equals your Toughness and Recovery together. But an Elder Gruff still gets +3, despite his Supernatural Toughness and Inhuman Recovery. Is this just a typo then?
That is not a typo, its just that the rules have successfully confused you.
While the catch
applies to all toughness/recovery powers, you only get the cost reduction to one of your powers (the highest cost one), and the final refresh cost for that power can't go to 0, it must be -1. You do not get a cost reduction to the whole package of powers, you just get it to one.
So for the Gruffs, their highest power is Supernatural (cost: -4), so at most they can receive +3 from their catch, even if the catch you design for them would technically give +4 catch. It doesn't matter that they have 6 refresh of toughness/recovery powers, the catch "rebate" is limited by their single highest one.
In short, if your highest power is Inhuman, no matter what catch you take its only going to be worth +1. If your highest power is Supernatural, max catch rebate is +3. If you highest power is Mythic, max catch rebate is +5.
You can house-rule it differently, of course, but them's the rules as written.