Can different wheel height affect the differential lock if the lock is not engaged?

Hello,
I'm lifting my 2007 TRD off-road and will put 295/70/18 tires under it. I have debated buying a full-sized spare tire, thinking that I could use the standard-sized 265/70/16 to slowly limp a couple miles if needed to get the flat tire fixed.
Speaking with a guy I know, he seems to think this would ruin the differential lock if I drove at all on different-diameter tires, but that doesn't make sense to me since the two rear tires rotate at different speeds when turning (and the lock isn't engaged).
Does anyone have evidence of the lock getting ruined by different-diameter tires? Any thoughts?
Thanks

 

As long as you don't engage the locker, it will be fine.