Article 100 Definition of Panelboard minimally seems to fit and it would seem that 110.26(E) restrictions that is applicable to any of these defined equipment would apply to the suggested installation pictured.
2023 NEC 100 definitions:
Service Equipment.
The necessary equipment, consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the serving utility and intended to constitute the main control and disconnect of the serving utility.
Switchboard.
A large single panel, frame, or assembly of panels on which are mounted on the face, back, or both, switches,
overcurrent and other protective devices, buses, and usually instruments.
Switchgear.
An assembly completely enclosed on all sides and top with sheet metal (except for ventilating openings and inspection windows) and containing primary
power circuit switching, interrupting devices, or both, with buses and connections. The assembly may include control and auxiliary devices. Access to the interior of the enclosure is provided by doors, removable covers, or both.
Panelboard.
A single panel or group of panel units designed for assembly in the form of a single panel, including buses and
automatic overcurrent devices, and equipped
with or without switches for the control of light, heat, or power circuits; designed to be placed in a cabinet, enclosure, or cutout box placed in or against a wall, partition, or other support; and accessible only from the front.
Motor Control Center.
An assembly of one or more enclosed sections having a common power bus and principally containing motor control units.
Depends here too. One breaker in a box can be considered just an "enclosed circuit breaker" and can be listed under UL489, the standard for circuit breakers alone. But if you were to want to want a "Service Entrance" rated breaker in a box, it would be listed under UL67, the standard for "panelboards", which is where SUSE is covered. But certainly as soon as you have more than one breaker in the box, it's no longer a UL489 listing.
Picture looks to be 2 - double pole breakers with GFCI.
