Ok a funny question of philosophy

We could go on and list a few dozen other inconsistencies all throughout the star wars movies, both, within one trilogy and the inconsistencies between the old and the new. If we really wanted, we could go for the thousands of inconsistencies in the expanded universe, too. Heck, I could even make a case for why the sole five lines of the Jedi code are contradictory, if one would, say, extrapolate them to philosophical constructs they quite easily may be referring to.

Now, on the other hand, we can also let it be and cherry pick the parts we like to adopt for ourselves. Why do you guess there are so many Jedi communities out there all with slightly different ideas, let alone the diversity here at TOTJO. Speaking of vagueness

For me its just representative of how communication can be more then the literal translation of words, and its use can change depending on the audience and situation. On one hand Yoda is talking to the son of Darth Vader, potential future Sith, hopefully future Jedi, but most definitely a beginner in learning of the Force.... and with the ObiKenobi exchange, its between two of the most highly trained Force users in the Star Wars galaxy at the fall of Anakin and rise of Vader.

Perhaps this highlights an interesting concept that a guru is not a god. So not only is someone's words always the same thing as that persons message, but also it might not be intended as a rule beyond its temporal application. Perhaps what we call wisdom generates different states of awareness and can be used to shape behaviour and learning by reorientation to logic, wonderment, re-balancing etc.

I think for Luke it was an exercise is mindfulness and focus to someone who was learning the basics. An important lesson in decisiveness but perhaps understood together which being seated in appropriate awareness.

For Vader it seemed to be a plea to Anakin that his perspective had turned entirely egocentric. As if ObiKenobi was referencing teachings on the difference between Jedi and Sith philosophy that they both were well aware, in the hope that Anakin would hear and understand it, to challenge the Vader within himself and re-balance away from the dark side to the light.