I would suggest lobster tastes worse when boiled alive. Any animal that has an endocrine system is likely to taste worse when boiled alive. My understanding is that adrenaline rush caused by immense stress eat up the glycogen stores in muscles which in turn prevents the production of lactic acid to tenderize the meat postmortem. I can't imagine this would be any different in lobsters than basically every other animal.
That stress / lactic acid / meat quality relationship only really applies to meat that's going to be aged, and it's as much about preventing microbial spoilage as anything.
There's no time for it to be a factor for lobster, which is going to be alive or frozen until right before you cook it.
Your premise may hold true in the general sense but not in the specific. I don't think lobsters produce adrenaline. There may be some other hormone that has a comparable effect though
