there is absolutely opinion and interpretation involved. the day of the week and direction of travel, for instance, may be indisputable facts, but when applying virtually any section, opinion is relevant. whether of the arresting officer, da's, defense, judge, or jury.
for example, you say that the torsion bar only assists opening of an ao toward the end of the action.
every ao i have seen is assisted once opening begins. it could be argued that the thumbstud is the mechanism which activates opening. a switchblade only opens "automatically" once some mechanism has been activated, not all on its own. it requires human intervention.
if someone believes this interpretation, the following language:
a knife that opens with one hand utilizing thumb pressure applied solely to the blade of the knife or a thumb stud
....becomes interpreted differently as well. since the thumbstud is not the sole "device" opening the knife, this exemption does not apply.
my other point was just to add some perspective. im not suggesting that an officer negligently arresting someone is appropriate. just that you are only focusing on one aspect of the vast array of laws that are enforced, and your interpretation of that law is not the only interpretation.
you seemed to be implying that unless you have said so, it is not "real law", but only a breakfast menu variation.
it is impossible to memorize the language in every code. often times the law must be referenced and discussed. if the officer decides the section is applicable, then the person is arrested/booked. if the court decides otherwise, then so be it, regardless of the avenue used to come to that decision.
does that make the arresting officer an idiot for having interpreted something in some way that the court has disagreed with? or that you disagree with?
no it doesnt. it is simply part of the checks and balances in the judicial system. very few laws are as black and white as you suggest.