Is it possible to put in too much: YES
Does the excess just leak out: Has for me so far. so YES.
Other than a bit of a mess, depending on where the tank is, Don't worry about it.
Now more:
I full time. This means that in the cooler season where temps are down below 40F (IE: Today) I have to add fluid because the fluid "Shrinks" when cold faster than the tank and the idiot alarm dings.
But come August when it's 101 in the shade. there is now too much in the tank and on the ground it goes. Not a good design.
