I'm actually okay with this.
It's very hard to get him into games while Seiya's locked into DH, so in the immediate term he's basically wasting a roster spot. And even when he's healthy it's tough to give all three of him/Shaw/Pedro decent playing time. Given that A) Mo can actually get some valuable development at Iowa (not so much at the plate but behind it) and B) the struggles of the infield mean you want both Shaw and Pedro around, it makes sense he drew the short straw.
Really curious who comes up in his place. Triantos just for pinch running?