From their docs it is "written in zig" which implies "all of it is Zig". They don't hide that they use JSC but they don't like to advertise either.
It is a bit manipulative advertising to draw hype people in I would say. You know those tech influencers who like to peddle stuff to get views.
edit: I was a bit unfair, it feels like those "hype tech influencers" are the ones who downplay JSC in favor of promoting Zig, not the project itself. The frontpage of Bun mentions JSC twice and Zig once.
It is a bit manipulative advertising to draw hype people in I would say. You know those tech influencers who like to peddle stuff to get views.
edit: I was a bit unfair, it feels like those "hype tech influencers" are the ones who downplay JSC in favor of promoting Zig, not the project itself. The frontpage of Bun mentions JSC twice and Zig once.