If the branches join at narrow crotch angles, ( a tight "V") rather than at wide angles, this will cause problems as the tree ages. If they are at wide angles, then you will just have a bushy-type tree. As long as you like the look, you'll be fine.

Yes, I agee: if they don't have tight V-shaped crotches, buy, plant, enjoy. Riverside Park in NYC has hundreds of Crabapples, and a few of them are mature, multi-trunked trees or single-trunked but branching within a foot of ground level. These are especially handsome standing alone as specimens.

Crabapples are so easy to love (and they love back, too.)