They don't even need to be on the same axis (although probably not really orthogonal in practice).

Async on-site work is entirely possible -- if you're working in a high-security place, or where the physical infrastructure is the point, or where you're building some physical object, it might make sense that work can only be done on site, but scheduling might be entirely up to you. Similarly remote but synchronous is easy to understand (calls, etc.). Another dimension is probably consistent vs. variable on both of those dimensions over time -- my ideal job is sync remote, sync in person, async in-person, and async remote at different times.