Well, they did provide a definition for "honest" - that it looks like it's built with the materials it's actually built with.
Of course, so did stone houses for centuries, and they still managed to look pleasing in the process.
I don't think 'honesty' (and 'functionality') are an improvement on the Vitruvian, 'firmitas, utilitas, and venustas'[2] for no other reason than Vitruvius backed the concepts up with examples and the examples included everything from fortifications to bridges to temples...which in map pretty well as typologies in which each takes priority over the others.
Perhaps it's because Vitruvius honored those generals, the city, and his gods rather than bricks.[3]
[1]: https://en.wikipedia.org/wiki/Opus_latericium
[2]: firmness, commodity, and delight
[3]: https://www.yatzer.com/even-brick-wants-be-something-louis-k...
It's not that I'm against modernist glass and steel. Bunshaft's Lever House sits on the same corner as Mies work and is one of my favorite architectural works. I'm not even against glass houses, though I think Johnson's earlier one is a better design than Farnsworth...if at least for not being built in a flood plain.