They looks to be _Thermal Relief pads_  to aid in manufacturability.

From some searches:
1. [Thermal Relief Design Guide for Your PCB](https://resources.altium.com/p/thermal-relief-design) for Altium
2. [PCB Thermal Relief Guidelines for Effective Layouts](https://resources.pcb.cadence.com/blog/2021-pcb-thermal-relief-guidelines-for-effective-layouts) for Cadance

Relevant part from the Altium article:
> A thermal relief pad provides a way to **keep heat confined to a pad** for mounting a component to a printed circuit board with solder. The pad for a component normally peaks through the solder mask, allowing solder to be placed on the pad during assembly. Some copper is removed from the edge of a thermal relief pad, allowing heat to be confined in the pad when applying solder during assembly.