If the last code block in the array passed to the 'for' operator is empty, the for-loop will run once, regardless of the condition. Exactly 1 iteration.

This works:
_number = 0;
for [{_i = 0}, {false}, {_i = _i + 1}] do
{

_number = _number + 1;

};

hint str _number;

Expected behaviour: Runs 0 times.
Actual behaviour: Runs 0 times.
Expected output: 0
Actual output: 0

However, if you empty the last code block it will run once.
_number = 0;
for [{_i = 0}, {false}, {}] do
{

_number = _number + 1;

};

hint str _number;

Expected behaviour: Runs 0 times.
Actual behaviour: Runs 1 times.
Expected output: 0
Actual output: 1

Another example:
for [{_i = 0}, {_i < 10}, {}] do
{

createVehicle ["B_MH9_F", getPos player, [], 0, "NONE"];
_i = _i + 1;

};

Expected behaviour: Spawns 10 MH9 helicopters.
Actual behaviour: Spawns 1 MH9 helicopter.

Yet another example:
for [{}, {true}, {}] do
{

hint str diag_tickTime;
sleep 0.1;

};

Expected behaviour: Infinite loop.
Actual behaviour: Runs once.