I should clarify that it's not so much that I can avoid getting punished as that we both make sure we've communicated about what's going on. So we talk and discuss until the point where either I've accepted that I deserve the punishment, or W recognizes that it really isn't fair and modifies the punishment.
Example: if I say something rude, and W responds by giving me 3000 lines (slight exaggeration). I will give feedback about why I think it's unfair (it will take me more than 24 hours to write that many lines). We then discuss our views of the severity of my offense, and whether the consequence is reasonable. W will generally acknowledge if she believes she was unintentionally harsh, and will modify the punishment accordingly (say, making it 300 lines instead).
Example 2: I walk out of the house in the middle of an argument. This both upsets and worries W. She responds by grounding me for 2 weeks, which feels unfair to me. I state my case, and she responds with a description of her viewpoint. She makes it clear to me how serious she is, and how much she wants to discourage me from repeating the behavior. I don't like it, but I accept that she is right, and comply with the punishment.
It occurs to me that both of those examples are non-spanking punishments. I have to admit that, with a spanking, the discussion tends to be less formal. If I'm getting a spanking that feels too severe for the circumstances, I'm likely to wind up getting pushed into a panic attack, and things rapidly fall apart because I've gotten triggered. Times when a punishment seems unfair, but isn't triggering, I generally discuss it with her afterwards, and explain what was going on for me, and why it felt harsh.
W and I spend a whole lot of time communicating about what's going on, and what is or isn't working for us. It's important to both of us that neither of us feels like something is unfair. It doesn't mean I can weasel out of things--we have a rule specifically against that!--but it does mean that we both value fairness and communication.
Ah well. I wrote a novel, and probably what you really wanted was sympathy with the venting.
As for whether or not I think it's lying... I'd say I'm about 50/50 on it. I don't think it's wrong to wait a bit before letting W know that something happened, but, as I said, I'm generally not punished for carelessness, and I do own up when I've broken a rule. I would personally feel concerned that something deeper was wrong, if I felt a need to lie and/or fail to mention things to avoid a punishment.
I'm curious: were you the one to initiate ttwd in your relationship, or was it your partners, or did you both enter the relationship with an interest in it? (You don't have to answer that one, I'm just curious.)