I'm not exactly 'comfortable' with it either, but it's a code that I have to abide by.
I have to agree with your points above. Yes, there are many 'good' sign fabricators that build a 'box' and use listed components like ballasts, sockets, wire, etc. They make a 'good' product..but, it's not a listed finished product. Yes, a UL label is not going to prevent the sign from being improperly mechanically installed, our building insp. has that job.
Yes, we have monster signs over here also, nothing like Las Vegas, but for here they're big.
Yes, the 'neon guys' use 'listed components' (that's basically the only available components to get their hands on); but...the installation of said 'listed' components is brutal! have you seen any neon components that were not listed? I see mis-use, no understanding of 110.3 (b); no concept of GTO strapped to metal window mullions; xfrs above ceiling tiles,etc.