Fact: 1 account = 10 character per server.
Fact: 1 account may log in 1 character at any given time when servers are up.

Let A = player A
Let B = player B
Let C = player C
Let D = player D
Let E = player E
Let F = player F
Let X = skill to play Single box
Let Y = skill to play Multi-box
Let n = number of accounts owned by player
Let G = 5 players in a group

Assume players A, B, C, D and E owns 1 account each.
Assume player F owns 5 account each.

Account Player functions
(n=1): A(n) = A = 1
(n=1): B(n) = B = 1
(n=1): C(n) = C = 1
(n=1): D(n) = D = 1
(n=1): E(n) = E = 1
(n=5): F(n) = F = 5

Group functions
G(A) = 1/5 G
G(A+B+C+D+E) = 5/5 G = 1
G(F) = 5/5 G = 1

Since players A, B, C, D and E player single box, they each have X skills.
Since player F multi box, he has Y skills.

G(A+B+C+D+E) * X = 5/5 G * X = 1 * X = X
G(F) = 5/5 G * Y = 1 * Y = Y

Question: Is X = Y ?
Answer: Yes.

Given in the Group function:
G(A) = 1/5 G
G(F) = 5/5 G = 1

We can say that one-fifth of G(F) function is the same as the G(A) function:
1/5 G(F) = G(A)


Assume the skill of A is equal of B, C, D and E.
If A = 5, them G(A) = G(F)

G(A+A+A+A+A) * X = 5/5 G * X = 1 * X = X
This is the same as
G(A) * X = 5/5 G * X = 1 * X = X
G(F) = 5/5 G * Y = 1 * Y = Y

Player A happens to be 5-boxing in Server 1, and it's the same person as player F in Server 2.
Therefore, X = Y.

So, G(G) = X skill to Multi Box