You might not be an addict, but does the distinction really matter?
Perhaps omission is different from lying, but is either any more or less hurtful and dishonest?
Perhaps watching porn isn't the same as cheating, but different people have different ideas of what cheating is. Some people are concerned with emotional cheating, some with physical cheating, and yeah some people consider porn to be as bad as cheating. Some people even take issue with so much as looking at another clothed person sexually, I'm not saying they are morally/ethically correct (it's all relative), but they have the right to their preferences in any case.
If you felt the need to hide it from her because you thought it would hurt her, then yeah that's not honest, and it will take some work to repair, whether you are "addicted" or not.
It isn't so important to find labels/comparisons for this or that, the fact is your wife believes you have been dishonest with her, and has a moral stance that is at odds with porn. You'll have to decide if her terms are fair. If you decide she is right then you can ditch the porn and work on sharing anything with her that you have felt the need to hide, if you decide she is wrong then it would still be a good opportunity to sort out your ground rules regarding sexuality and honesty.
If i can provide an example. If your wife went to a male strip club once or twice a week, would you be okay with that? Sure she isn't physically or emotionally cheating, but would it bother you? What if she knew it might bother you but chose to hide it from you so she could have her cake and eat it too?
Or even if it doesn't bother you, wouldn't you prefer that she didn't feel the need to hide it from you?
Know that i'm not just crapping on you here. I'm a young guy who is lucky enough to be finding out now that many women have a problem with porn. If I hadn't read some of the accounts from partners here, I might have wandered into a relationship with porn as a trusty sidekick, and never have thought anything more about it.
So I get why a lot of guys don't consider it to be a problem, and if you weren't trying to hide it from her then it wouldn't dishonest so much as naive. As well, someone who has a problem with porn and doesn't make it clear to their partner, is failing to hold up their side of the honesty agreement. Honesty is the responsibility of both individuals in a relationship, and purposeful omission is just as dishonest as lying. There are many things that make up the spectrum of dishonesty, not just lying
On another note, it's rather interesting that you and a partner who recently posted here have both been married for 13 years...