horse collar harness instead of a yoke?

It’s not a dumb question. An ox can’t just be put in a common horse caller and work well because a horse and ox are built different. As Droverone stated historically some people did use modified or purpose built leather collars and harness on oxen. From what I can tell it seemed to be most popular around Minnesota, North Dakota and the corresponding part of Canada. Oxen have also been used with Head yokes, Forehead yokes, Wither yokes, Shoulder yokes and various other types of collars. They all have their pros and cons and none can claim to be the best for all things. It is critical that a teamster understands the design construction details and fit of what ever system they use. When the shoulder yoke is designed, constructed and fit properly it works very well. Historically it was popular because leather was scarce and wood was plentiful.