Why is Yorkshire split up into North Yorkshire, South Yorkshire, etc., and does that mean that 'Yorkshire' isn't a single county like Kent or Lancashire?

It seems that the modern history of the divided county might have some roots in ancient divisions:

Yorkshire originated in antiquity as the Kingdom of Jórvík. It was traditionally divided into West, North and East ridings. The term originates from Old Norse þriðing, "third part", a legacy of the area's ninth century Scandinavian settlers. Each of the ridings was then further subdivided into smaller units called Wapentakes, which were administered by an early form of democratic representation termed a "Thing". Later the wapentakes were used as the basis for administration.

Here is a more modern incarnation of the divisions:

The borough corporations of Beverley, Doncaster, Kingston upon Hull, Leeds, Pontefract, Richmond, Ripon, Scarborough and York were reformed by the Municipal Corporations Act 1835. In 1889, as part of the Local Government Act 1888, Yorkshire was divided into administrative counties (each with a county council) and county boroughs. The administrative counties closely followed the ancient ridings, with the exclusion of the large towns of Bradford, Halifax, Huddersfield, Kingston upon Hull, Leeds, Middlesbrough, Sheffield and York. Yorkshire continued to be classed as a single county under the act, although each of the ridings retained their own lieutenancies and shrievalties. York became associated with the West Riding for this purpose.

https://en.wikipedia.org/wiki/History_of_local_government_in_Yorkshire#Ancient_divisions

On the subject of Ridings, it is worth noting that Tipperary is divided into two 'thirds', and Yorkshire currently claims four. The county of North Yorkshire, The Metropolitan County of West Yorkshire, the ditto of South Yorkshire, and the East Riding of Yorkshire Council. North, West and South do not use the word Riding, so if you discount them that only leaves one.....

Yorkshire was not the only county to be divided. Sussex still is divided into East and West. Lincolnshire was divided into three Parts, the Parts of Lindsey, the Parts of Kesteven and the Parts of Holland. To make matters more complicated, the Parts of Lindsey was subdivided into three Ridings - North, South and West.
https://en.wikipedia.org/wiki/Riding_%28division%29