I agree, the riff resolves differently which gives it a different feel.
Incidentally, Clapton does a pretty close copy of the Stairway riff in his song Let It Grow. Happens around the 1 minute mark:
https://www.youtube.com/watch?v=YpDlmop0uYU
Clapton later said he copied it subconsciously.
Interesting. I’ve heard that song before and never made the connection.
Happens all the time in, nothing to litigate, just move on.