You guys are all missing it. Forget about what moment Vader is referring to in ANH. That doesn't matter. What matters is that he made the statement to begin with. He wouldn't say something like that unless it was the first time they've encountered each other since their falling out.
This.
The whole Vader/Obi confrontation in the TV series should never have happened. And Obi-Wan should never have been running around with 9yo Leia. Etc. It's all just damaging the franchise for a quick buck.
'Rogue One' is the correct way to dabble in the timeline gaps. They made a good quality movie that filled a longstanding plot hole and didn't undermine anything important.