It is unclear, so the table needs to decide
Unfortunately, this mechanic of the Echo Knight is incredibly unclear as to how to adjudicate these things for moving it. I have reviewed other potential similar mechanic like spiritual weapon or telekinesis, but none of those have the same properties of the Echo Knight.
Which leaves us with a giant shrug as to what to do. In these cases, it comes down to the player talking to the DM about what they feel is fair, reasonable, and fun. There is no 'wrong' answer here, but you should think about the potential consequences for each decision.
Looking at how this might affect gameplay of movement, positioning, and battlefield control, it's important to think about the edge cases - but you're not going to cover them all. And that's okay! When they come up, discuss together and be reasonable. If the DM provides an unhappy result, table the argument until after the game and discuss why you didn't like it and what you think a good compromise could be.
Prepare in advance
Given the lack of clarity about this subclass in general, if a player is considering choosing it then they should discuss these issues with the DM prior to playing. Making sure everyone understands the gray areas, what ambiguities need to be agreed on, and that judgments may come up that require an immediate ruling will go a long way to to mitigating any unhappiness and setting the expectation that this subclass is a little loosey goosey.