I assume that "similar look" here means they coordinate their outfits while leaving just enough room to deny the appearance of dating each other.
Not exactly.
"Similar look" is more like you share the same general color tone or motif in your coordination. However, this tone/motif is often just one part of what you share or just the general coordination that makes people think you are sharing the same coordination. In other word, you look like you are similar to each other, but your clothings don't exactly match. For an example, if one wears lightly colored T-shirt and jeans, ther other would also have lightly T-shirt and jeans, albeit a different color of T-shirt and darker jeans.
Mean while, "pair look" is fashion coordination that is the exact same motif. Meaning, if one is wearing a heart printed shirt, the other would also have heart printed clothing and the hearts would look the same. While the exact coordination can create a contrast between the two of you, the motif you share is very much the same.
Basically, "similar look" is the toned down version of "pair look".
That's the best I can do at understanding it and explain the two concepts. To sum it up, both are just clothings that look like each other kind of thing. But well, though the amount is different, it's hard to put a pin on it if you see it for real. So yeah, I don't think you are wrong. But not too exact either.
