Yes, that's what they told us.

The truth is not this one.

Arena, exactly as all the others features in the game where you can't assign the equipment uses the by default equipment stats.

If you are not an overstacker or if you are in a relatively new server (and this is where this legendary folklore was born) this basically is almost the same thing as dividing by 4, but if you are an overstacker (and who is not?) then this ceases to be a situation alike.

3vs3 arena showed this blatantly.

For 'by default equipment' i mean the equipment you got in the exact order you actually got it the first time while doing the plot missions that unlock it.

Since we all move the gears accordingly to our preferences and necessity, after some time your actual equipment is no more the original one (mostly happens due to purifications, generally when you get a better purification on a level 6 or lower refined piece of gear you move it on move 1 and you bring that one to level 8+ in the place of your original piece of gear and you also apply to that piece your best charms).

If you want to know what is your by default equipment do this simple task.

1) remove all the equipment from all your ninjas

2) remove 3 ninjas from the field and leave your main only there.

3) move your main on the field.

4) add a ninja (lets say sakura)

5) add a second ninja (lets say sasuke)

6) add a third ninja (lets say naruto)

The equipment your main will get after you followed this procedure will be your by default move 1.

The equipment on sakura will be your by default move 2, on sasuke your move 3 and on naruto your move 4.

This is what sets your initiative in matsuri, arena, survival trial, etc...

For arena, specifically, since your main is by default there and you cannot remove it, then the 'by default' move 1 set of gear gets applied to it, so the ninja that is actually your real move 1 in arena gets geared with your 'by default' move 2 gear (so in most of the cases, unless you run a shark bomb team... You got it, i suppose).

Ranked battle and space time are different because they consider your actual implement equipment at the moment you entered in the feature and every time you fight there it records your newest gear situation.

Obviously, this starting situation gets modified by treasure tools and assist cards, but what they modify is the by default situation.

In general you don't see big differences between the theory of the total initiative divided by 4 and the truth unless you moved a lot your gear and unless the difference between your total initiative and the enemy initiative is lower than 4 times the difference between your move 1 treasure tools+assist cards and your enemies/allies' ones.

But when this happens, and is quite common in servers as old as mine, you may see in 3vs3 arena weird behaviors that cannot be explained otherwise (like, for example a friend that has 20k total initiative less than you and a treasure tool in move 1 4 levels lower that moves before you just because runs a shark bomb team, or a big whale move 3 that moves before your move 2...)