Walking more than 100K (and not just more than 50K) does give more stardust, and it can be multiplied by 1.5 using a Star piece!
And this is only from the weekly reward, not counting that I went ahead and accepted gift, etc. to get more stardust while my Star Piece was active
Walking more than 100K per week has never been so rewarding, I hope it was every week like this!