I get that hindsight being 20/20 you are under the impression that they should have "known" what was potentially going on with that neck, but that's not entirely realistic or reasonable from the perspective of a builder. I've been building for years and have built many guitars and basses. This neck separation issue has literally never happened to one of my builds without significant accompanying impact damage. It's not a commonly occurring issue as there's little mechanical cycling that goes on with an instrument that will lead to this kind of delamination of the glue joint.
If someone contacted me about a finish line or potential delam down near the heel of the instrument, I would also presume it was much more likely to be a finish flaw (possibly finish not adhering to a razor-thin line of glue in the joint) than a structural issue. And no offense to you, but in my experience, consumers and players of musical instruments exhibit a lot of magical thinking around their instruments compared to builders and techs, and so I often have to be cautious when working with people's assumptions about what has happened to the instrument or the issues they are having with it. I mean that with total respect to you as a consumer/player - it's my job as a builder to figure out what a customer wants and deliver it, and sometimes also to address a misunderstanding with a customer as well, but I don't consider it the customer's problem or the customer as the one to blame.
I'm not defending their communication pattern or how they approached fixing the issue, as I'm small and meaningless enough to have taken it back, repaired it on my own dime and maybe split the difference with you on shipping only. I'm only pointing out that it appears that some of the disappointment on your part is stemming from your assumption that they 'should have known' and should have given you opportunity to address it with them earlier before this occurred. In my own case, I bet I would have done that. But at the same time, I would not have assumed a structural issue and I probably would have approached it like any finish repair and only addressed that issue. At some point down the line the fingerboard may still have separated for reasons unbeknownst to me at the time. Just some food for thought.