This is a deliberate choice by the designers and we had some to and fro with them about it for the application we were building (a complex 40+ question process

This is a deliberate choice by the designers and we had some to and fro with them about it for the application we were building (a complex 40+ question process for exports). They seemed open to more questions per page where needed but their single page per question standard makes sense when you understand the need to support the whole audience for a lot of their sites. Stats suggest over 16% of adults in the UK have very poor literacy so in the interests of accessibility I think the page per question is a reasonable pattern.