I'd say the original already isn't ambiguous: Kenobi directly tells Luke that Vader murdered his Father. The "from a certain point of view" scene had to be added in ROTJ to explain away the retcon.

Ben Kenobi does pause in a pregnant way right before delivering the fateful line. In a way that almost looks like he's thinking about how to hide something. It works perfectly with the later revelation.

For reference: https://m.youtube.com/watch?v=hFB16GCocfw

It's crazy that essentially the entire Star Wars canon is built on one piece of dialog by Alec Guinness. (Not just Anakin/Vader, but the Force and the events around Order 66)

The face he makes at 0:56 does look like the face of someone who's trying to come up with a lie.

More likely it would just be left to the fans to come up with their own justifications for the retcon, like most other inconsistencies in Star Wars.