Giving Webster the benefit of the doubt, I think he has made a tactical call, which has evidence to support it, that TMM and SJ don't work well together. They both prefer to play as "#1 playmakers" and TMM has been noticeably poor when playing alongside SJ. CHT is like Metcalf in that he plays more direct and is a more natural contrast to, and therefore halves partner for, SJ.
I think Webster is saying that the problem isn't SJ, it's the SJ/TMM combo.
Of course none of this answers the question of whether SJ or TMM should get that #1 playmaker gig....and I'm certainly open to the argument that it should be TMM.