Well the issue with Thancred side of things is that he still had 5 years with Ryne by the time the story began for WoL.
The others only been in the First for 3 year or less. Lack of understanding Thancred's change of heart and acceptance of Ryne can be more contributed to the fact we did not get much detail of those 5 years nor get to see how it proceeded since he grew to accept Ryne as a family member and as a another person during that moment but never got a chance to say what he wanted to say due to it developing into being more of a personal struggle that there may not be a way to save them both. This is one part of the story that I felt should have been included but they cut it down to those small moments in Shadowbringer and hide it until the very end when Ryne and Minfillia had to make a choice for REASONS.
They could have included moments in Shadowbringer where WoL had a chance to talk to Ryne or Thancred once in a while through the course of 5.0 MSQ during their breaks and get Echo visions to see how Thancred and Ryne developed through the process of the 5 years so players can see how Thancred started out as someone who only say Ryne as another Minfillia or her replacement into being a daughter figure and another person he valued as a family.
