I've seen plenty of suppliers (often on eBay) use the term too. That doesn't make it correct.

Fully contained one-piece headlamps were termed sealed-beams (GM called them "guides"). They were round. Stylists wanted more so in 1975, the rectangular sealed beam was introduced. To create more customization, unique shaped lenses were made and fitted to matching reflector buckets that held a separate replaceable bulb. These were termed "composite" type for their multiple sections.

The composite lights assemblies are unique to the car but the electrical bulb had to be standardized for economy sake. Europen halogens are the "H" series and US DOT approved bulbs are 9000 series. The bulb's physical shape got it the term "capsule". I quick look at the parts will shed light on the subject (pun intended).