I can confirm this is the same as Issue https://github.com/ValveSoftware/steam-for-linux/issues/306. I also use Primusrun/Bumblebee to start Steam. I just checked to see if I would get the distorted logo if I ran Steam without Primusrun, and the logo showed up properly. I will post full info and screenshots at https://github.com/ValveSoftware/steam-for-linux/issues/306.
When starting Steam with optirun/bumblebee, the steam logo is highly distorted, or otherwise corrupted to an elongated rectangle outline. Attaching screenshot. Logo is fine when launched without optirun/ with the intel gpu. Same system info as my other issue.