No.
It doesn't say "an amount equal to the enhancement bonus".
It says "enhancement bonus"
An enhancement bonus is not a number, it is an enhancement bonus.
Do you disagree with this statement:
An enhancement bonus is an enhancement bonus]
?
Otherwise, when an implement says that you add it's enhancement bonus to attack rolls and damage rolls: well, it doesn't say you add it's enhancement bonus as an enhancement bonus, so it must be an untyped bonus right?
Same with neck slot items clearly...
I had a whole section written here to respond to this, then decided it was wrong and started over because in the end we're fighting over language. What I realized is that we're debating the definition of "Enhancement bonus" as used in the rules text as I will illustrate below.
There are two basic uses of the phrase "enhancement bonus" within the rules and only one use of the word "Enhancement" by itself.
Magic items have a template entry like this:
Enhancment: +x (text here about what the +x adds to such as AC, Fort/Will/Reflex, or attack rolls and damage rolls)
As for "Enhancement bonus" it is used to describe a type (such as PHB p 275 where it talks about bonuses and penalties) and it is also used to describe a quantity (such as PHB p 276 where it talks about possible modifiers to a damage roll and in any magic item where there is a property giving a bonus. As an example a "Dread Weapon" has this:
Property: On a critical hit the target takes the weapon's enhancement bonus as a penality..."
Now penalties are never typed (at least according to PHB 275), but this reference is about the quantity of the penalty and not the type.
Another example is the dreaded "Staff of Ruin"
Property: Whenever you make an attack using this staff, you gain an item bonus to the attack's damage rolls equal to the staff's enhancement bonus.
Again this is clearly referring to the quantity of the bonus because it is clearly declared as an item bonus.
I could argue that because of
the lack of a specific declaration of bonus type in DIS that it is therefore untyped, but I'm not sure if that is really any better than your assertion that it's wording means
both type and quantity. This way leads down the road of what is an "Attack" and I don't care to have that debate today.
Therefore...I'm with Nifft. It can be read either way by RAW without further errata/FAQ. It should be noted that I still think your reading is incorrect. I'm more inclined to believe that "enhancement bonus" is used as either type
OR quantity, but not both at the same time. Hence I have to disagree with your assertion "An enhancement bonus is an enhancement bonus".
Of course, that's all irrelevant anyway, because using Dual Implement Spellcaster with a single quarterstaff was never legal by RAW
A Quarterstaff can be a double weapon, which makes it behave as two weapons when used as a weapon.
It is not a double implement, it does not behave as two implements when used as an implement.
DIS requires that you use an implement in EACH hand, not an implement in BOTH hands. This means that (as there is no such thing as a double implement) you must use two implements.
I already agreed that you should need Staff Fighting to use a staff this way. However, a staff works like any other weaplement. You're treated as having a staff in each hand and since a staff IS a weaplement....well you should know the rest.
Interestingly, CB (which we know is not a rules reference) allows you to get DIS without Staff Fighting if you equip your staff in both hands. Also interesting is that you can get the bonus to spells for two-weapon fighting and two-weapon defense without Staff Fighting. Perhaps staff has some special exceptions we don't know about or maybe it's implements...or maybe CB has some more bugs.
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