I feel like we need some clarification about what "consistent" means here. If we're talking about having the typography shown to user A look exactly the same as that shown to user B, why does that matter? (And why do the major font rendering differences between Windows and macOS not matter?)
If we're talking about having the typography on user A's phone look the same as on user A's desktop, that seems a bit more reasonable, but the rest of the UI is necessarily going to be drastically different save for perhaps the color scheme.
Or is the "consistency" that matters here about making sure the website is pervasively using the same typography as the advertisements?
> If we're talking about having the typography shown to user A look exactly the same as that shown to user B, why does that matter?
Well, I suppose that's a valid question, but it's moving the goalposts. We were talking about having consistent fonts, and I'm claiming it's absolutely possible by using web fonts (after all, that's the reason web fonts exist).
If we're talking about having the typography on user A's phone look the same as on user A's desktop, that seems a bit more reasonable, but the rest of the UI is necessarily going to be drastically different save for perhaps the color scheme.
Or is the "consistency" that matters here about making sure the website is pervasively using the same typography as the advertisements?