Blimey, I might be agreeing with Pete S on here. I think that Bobby Sanders or whoever it was put Ray Agee in the studios and said summat like " Let's try you out as a soul man on this swingin' Detroit type of backing track we've laid down'. It is so vastly different from the 1,000 other records he made, I do think it is an anomaly. I think Mickie Champion was similar and I was going to disagree about Ray Charles but then realised it's written by Ashford & Simpson so of course it's Ray updating himself for the young black crowd. If he can give country a go, he can certainly try the soul thing out.
I think for our purposes R&B should be blues with a rhythm rather than soul songs by blues singers but there's 1,000s of instances where it is down the middle.