Earlier quoted context omitted.
1: Am I under arrest? 2. No. 1. Okay, I'm going to walk away now. 2. You can't do that. I'm asking you questions and you are not free to leave. 1. But you just said I am not under arrest. Are you arresting me? 2. No. 1. Okay, I'm going to walk away now. ... [a few iterations later] ... 1 starts to walk away. 2 informs 1 that s/he is not free to go. 1, on the basis that 2 has said s/he is not under arrest, and tired o…
This is needlessly complicated; instead, I offer: 1. Am I free to leave? 2. No. OK, now you've made it clear you are under custodial interrogation (I suppose there are safety exceptions to that), Miranda is invoked according to the Orin Kerr, and you can keep your mouth shut beyond the requirement to give your name in some states.
There was a video a few months ago showing someone recording in-country immigration checkpoints (dozens of miles inland, checking IDs without cause in a very unconstitutional manner). The driver reiterated "am I free to go?" until he got a "yes". Chilling, and informative that "am I free to go?" is the ONLY thing you say/ask. If they say "no", lawyer up & shut up; if "yes", leave.
Only question remaining is at what point does the LEO's refusal to say "yes" or "no" constitute one or the other.