Complete sentences in the book:
Note that it says "when" and not "before". This indicates that pivoting is part of the move.When the model moves, first pivot about its centre to face the direction you wish to travel.
This is important for later on.
So, as per the rules, this is what would happen with your abom-block.if the move is found to take the unit into contact with an enemy, then it counts as charging, and this is resolved using the normal rules for charges and using the distance rolled as its charge range.
You move exactly one inch away. The abom pivots and hits you. Then the abom rolls the dice to determine its movement. Then you would measure to see if the random movement would take it in to contact with the unit, then you would charge said unit.
However, later in the rule this is said:
This doesn't say "unless the model would come in contact with the unit, in which case it counts as charging." And this does support your argument - sort of. I can't argue implication, since this flat out contradicts an earlier part of the rule, but i can point out that the word "forward" is never used at all. This implies one of two things:if the random move brings the unit to within 1" of a friendly unit or impassable terrain, it stops immediately and cannot further move in the movement phase.
1) If the model can make contact, it can get within an inch.
2) Models with random movement can never get in to base contact in their own phase.
This is a silly argument. We all know the writer's intention. If you want to argue the second point, feel free, but that doesn't depend on you being within an inch at all.
Unless you can point me to the word, "forward movement" at all in that rule.