I certainly agree that a "safe legal merge" means you are far enough ahead of the other vehicle. Just like when you are driving a car and pulling out into traffic from sitting stopped at a stop sign waiting for a gap big enough to safely pull out into. You can't just pull out and if you manage to get your car out into the lane before someone slams into you from behind tires squealing it their fault not yours, don't work that way, and you do have to give the other vehicle enough room in order to safely merge into their lane ahead of them.
My point with the second incident in the video that JoeyBike shared was that there was fault on both sides. Although judging distance in videos can be deceiving due to different lens effects it looks to me like the blue truck/SUV at one point was far enough ahead to safely merge over into the bike lane preparing for a right hand turn in front of the cyclist and the cyclist would probably have had to stop pedaling and apply a little bit of brakes but that would have been all of it. The heavy vehicle, however, failed to merge over when they could safely do so when far enough ahead and instead stayed in the lane to the left of the bike lane and slowed down in it which allowed the cyclist in the bike lane who was not aware of the turn signal and proceeding at a steady pace to close the distance so that when they finally did turn after having the turn signal blink for a while they turned right in front of him right across his lane.
If the driver of the blue truck/SUV had instead merged over when they were safely far enough ahead to do so and then slowed down after merging in preparation for the turn only a very distracted or obtuse cyclist would have continued to maintain pace try to slam into their rear end or pass on the right (would have been a real pass on the right if the cyclist would have had to move to the right of the bike lane to pass a vehicle in the bike lane on its right side).
Errors on both sides came together to produce that second near miss. If the heavy vehicle driver would have safely merged over when they were far enough ahead to do so (from my looking at the video that would have been at about 1:07 to 1:08 time stamp, close but do-able at that time stamp if the heavy vehicle driver had merged over then and then applied the brakes after merging to slow for the turn) then the cyclist unless very distracted or very obtuse would have been able to apply reasonable braking action to avoid a problem. An annoyance and an inconvenience most certainly and possibly resulting in a few mutterings under the breath about getting cut off and shoving four tires up someone 4-wheel drivers fat rear but not a bad near miss situation like what did happen. It is also true that the cyclist failed to notice the turn signal and the "body language" movements that the heavy vehicle was making in advance of the way it made its right turn that would have allowed the cyclist to avoid the situation even without the heavy vehicle driver performing the turn correctly and first safely merging over into the bike lane far enough ahead of the cyclist and then braking gently and making the turn.