Humberside is a geographical term....East Yorkshire is a Riding of Yorkshire, an Administrative area (but is also a geographical term).
Mates of mine live in Dunston, Tyne and Wear, but geographically, they live on Tyneside.
Hull is on Humberside (as are Hessle and Barton - on - Humber), geographically, but is also in East Yorkshire, even though it is a City and is self-governing.
It's all effin confusing!