tux_ The project has repeatedly said that the first Motorola device or devices would be flagship. Those tend to be expensive and gigantic and have 47 cameras plus an ectoplasm detector. The project has also repeatedly said that after the release of the first device there is room to hope for other devices -- though for a while they will need to be devices with premium processors to get the necessary security features.
Small devices with premium processors are a bit unusual, because premium processors are expensive and many people aim for small devices to save money. That said, in a year or two processors that are premium now may well be cheaper.
TL;dr: the GrapheneOS project has been pretty clear about the first device(s) being large and expensive, but it is not particularly expected that all future Motorola devices supporting GrapheneOS will be large and expensive.
https://m.youtube.com/watch?v=ovoBi3pXD_A