Yeah, the eye color thing is real, that one caught me out, but there are physical similarities between twin flames and appearance changes happen too.
Twin flames often share physical traits, but their eyes usually start differently. The idea is the soul split expresses shared energy uniquely through them, as the “window to the soul.” As you progress toward ascension, eyes are one of the biggest changes. One twin’s often shifts more toward the other’s color, usually the more empathic one.
They might meet in a shared middle, or Blue Ray twins end up with crystal blue eyes and thick black limbal rings. My blue-green eyes turned pale blue with rings post-union, one eye first (heterochromia for a bit).
You’re not imagining it. Same as voice shifts and mirroring mannerisms, or body temp changes nearby. Eyes are just the most obvious.