Shelties are pretty smart dogs so I doubt a "different set of poles" will make a difference to him. Honestly, if dogs had such a hard time with different poles or striping it would make trialing near impossible to Q because you may not see the exact same 'look' on the poles a different trials. You want the dog to be exposed to different 'looks' so they learn they have to perform regardless of what it 'looks' like.
This is what I was thinking too. I think the instructor's dogs aren't as smart as Shelties. There's another Sheltie in class and she commented last week about how smart both are.