El Torro wrote: I'm not even sure why
GW have gone down this route, seems to be just because they can.
It's partly 'because they can' and partly because
GW's focus is on making pretty looking miniatures first, and a game second.
When you're designing for a game, at least one where the size of the base matters, making sure that a model fits onto an appropriate sized base for the unit type it is intended to represent is an important consideration when designing a model.
When you're designing pretty miniatures, the sculptor has more freedom to just make the model look how they want, and then you slap on whatever sized base best fits the end result... assuming you have the ability to make said base.
Until relatively recently
GW, like most other manufacturers out there, was constrained by the fact that manufacturing budgets were generally better spent on producing more models rather than expanding their base range, and so they designed their models to fit their range of bases, even though that sometimes meant limiting models to a certain size, or a certain type of pose. But these days, they have the range and apparently the resources to allow them to just whip up a new base when they want it, and their focus on designing for aesthetics rather than game role means they frequently want it.