Yeah it didn't really do that at all.
It kinda did. If you look at all the evidence, it'S pretty telling.
- Different logos in each timeline. We specifically see the old style during the young Ford scene, establishing it as an older design.
- Talk of an incident 30 years ago in one timeline, and not the other.
- Talk of Arnold's death by an outsider in one timeline, and not the other.
- Logan says his company are looking at buying the park, because its suffering since the death of Arnold. That doesn't take 30 years to materialize, therefore, Logan and William's story is set not long after Arnold's death. The modern park is not one in "freefall". Ford comments on how many executives he's seen come and go; there's a longevity to the place that isn't present in the William and Logan scenes.
Fundamentally, the Westworld the MiB is visiting is in a very different state to the one Logan and William are in, and that's all revealed through the dialogue and subtle clues in the background.
It doesn't definitely prove MiB is William, but Williams arc seems to be heading to that conclusion, but in terms of more than one timeline...that seems nailed on, or rather, what the showrunners want is thinking.
Through Dolores though, we're actually seeing ATLEAST three timelines.
Edit: To clarify; I think we are seeing various loops Dolores has been on, leaving clues and reminders along the way. Hence seeing herself in the crowd, the mystic etc. The William storyline is an integral part to her discovering the self-enlightenment found in the center of the maze. The path she's on is merely a physical journey that will give her the necessary mental prompts to catch up to where she was before, making progress each time she embarks on her personal quest. Might be why it has taken 30 years.
Think Edge of Tomorrow, learning from our mistakes, and the tattoos in Memento, in terms of leaving yourself clues.