Mono as chrome is the arrangement most products reach for. The interface reads as instrumentation — the chips and the join button feel like controls, and the description reads like an ordinary app paragraph. It is legible and it is also anonymous: swap the logo and it could be any listings product.
Mono as voice puts the texture where the writing is. The description reads like it was set rather than rendered, and the controls recede into plain Diatype, which is what controls are supposed to do. The cost is density: Semi Mono runs about a third more lines for the same copy, so long descriptions need the tighter step or more room.
The question the page is really asking: should the mono be a property of the interface or a property of the writing? Everything else follows from that.