I had someone try to convince me that Young Lust counted as progressive rock because Pink Floyd performed progressive rock and The Wall was a progressive rock album.
Not a persuasive argument, but a memorable attempt for sure.
65daysofstatic - "retreat retreat" and "sister." One is definitive post-rock, plus an uplifting anthem for the band. The other is a slow, foreboding ambient electronic piece. No shared instruments, themes, or genres between the two.
Bright Eyes released the albums "Digital Ash in a Digital Urn" and "I'm Wide Awake, It's Morning" on the same day. They sort of answer this question where you can tell the artist was split on two different creative strands.