I think the burnline definitely affects flavor. As that ratio of wrapper to filler get's distorted, so do the flavors contributed from each leaf.
On R/H, even 65 for some of my CCs can be a bit too wet. I actually find the most consistency and optimal flavor at around 62. As for storing at 70, then bringing them down to 62 to smoke, I question how well the cigar has adjusted to the lower R/H. I think it takes a long time (months upon months at a minimum) for a cigar to evenly adjust and stabilize with the broader R/H measured from the air. Water transfers quickly and easily through a gas, but very, very slowly through a solid piece of mass.
In fact, I suspect the variation in R/H within the stick is why you had burning issues. The wrapper and binder elements of the exterior of the cigar had probably adjusted, as had the foot, but once you had delved 1" or more into hte smoke, you had all kinds of varying moisture affecting the burn. Same effect happens when I travel with cigars to a humid place.
When I went to Puerto Rico earlier this year, I actually cut 3 or 4 of the sticks I planned to smoke over the next few days, and dry-drew them a few times a day to bring the local R/H through the entire stick. I actually had great success with minimizing typical burn issues like tunneling, that usually happen when I travel to a real humid place. Usually, even a minuto will be trash half-way through, impossible to keep from tunneling and turning bitter.