Dies to Removal

So I a playing FNM Sealed and my opponent has Hundred Handed One. I have many flyers ready to swing lethal, and my opponent is short one mana to Monstrosity his dude. He tries to play a card I can't remember that puts a +1=1 counter on it and claims the reach ability is Activated due the counter activating Monstrosity. I counter it anyway and kill him. My question is on Monstrosity static abilities being activated by the +1+1 counter? I claim Bull shit as the ability says "when it become monstrous".

You claiming bullshit was correct.

The shop owner claimed that Wizards said it works, but I have yet to find said "Wizard's Ruling". The way I read it; Monstrosity should be activated to become Monstrous (should read "has Monstrosity", but no one asked me in development) in order to receive said static abilities. +1+1 Counters are just icing on the cake and not the means to monstrosity.

701.28. Monstrosity

701.28a “Monstrosity N” means “If this permanent isn’t monstrous, put N +1/+1 counters on it and
it becomes monstrous.” Monstrous is a condition of that permanent that can be referred to by
other abilities.

Monstrous isn't a static ability, it's just a description of a characteristic of that monster. You are correct on calling bs. Monstrosity is under Keyword Abilities in the comprehensive rules. It's also an activated ability. Merely putting a +1/+1 counter on it doesn't give it monstrous.

The original wording of monstrosity in design was 'once per game', the +1/+1 counters were added to help with the memory issues, but theoretically are not required for a monsterosity ability. By adding +1/+1 counters to it solved both the memory issue and allowed for simpler common monsters that would not be red flagged by NWO.

So technically they could have done
Steve (r)
Creature - weasel
(1)(r)Monstrosity 0.
When steve becomes monstrous it deals 2 damage to target creature or player.
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