He's interpreting TM p309 (Calculate Anti-BattleMech Battle Rating) as the rule that allows it.
"If the unit can perform leg or swarm attacks, add the BV [of the weapons again.]" He believes that he can choose to not add this BV during BV calc, thus reverse-designing "cannot perform AM attacks" into the platoon.
The problem is that the rule does not specify how to determine if the platoon can or cannot perform A-M attacks; default is right in the book: foot, motorized and jump platoons can, while mechanized platoons can't.
Tac Ops introduces armour kits that prevent foot, motorized of jump infantry from making A-M attacks.
Outside of this, there is no step to determine is a PBI unit can or cannot do A-M attacks.
You're right; he's reverse engineering the rule.
Let's see if putting it this way makes more sense to others:
A) if you are taller than 5'8" you get a bowl.
b) if you are 5'8" or shorter you don't get a bowl.
c) those who get a bowl get to choose the bowl's size, between 1 (smallest) and 9 (biggest)
d) those who have a bowl MUST get water for the bowl - they also get to drink from the bowl whenever they please.
e) those without a bowl cannot get water at all and can never drink water "outside".
Note that if you are taller than 5'8" you get a bowl. Period. You can choose the smallest size and thus carry the lightest load of water, to the point where drinking from the bowl is next to pointless. There is simply no mechanism or rule that states that you cannot take a bowl.
You cannot be 5'8" or taller, choose to not get the water and then claim to not have a bowl; getting or not getting the water is dependent on having a bowl (which is dependent on height); not the other way around.
Of course, you could get to wear a raincoat, in which case you have to turn in your bowl as an
explicit exception to the height requirement.
I'd posit that Herb did not, in fact, answer the question: he stated, essentially, that having a bowl or not is dependent on getting the water.
Jim's question was: "When constructing a foot infantry platoon is it required that they be designated as anti-Battlemech infantry (incurring the extra BV cost as outlined on page 309) or can I declare that they are incapable of making a anti-Battlemech attack."
Bare bones: "Does a 5'9" guy HAVE to get a bowl? or can he CHOOSE to not take a bowl." (A y/n question)
Herb's answer was: "If you don't pay the cost for anti-Mech capability, then they are incapable of anti-Mech attacks."
Bare bones: "If you don't get water in your bowl, you don't get to drink water "outside". (Not a y/n answer AND not even addressing the question posed)