Sunraysia Hwy distance signs

[z386x]

I remember reading somewhere many years ago about a reason for this but I can't find it, but pretty much when the alpha rollout happened in the late 90's pretty much all distance signage (like this one for an example) for B and C routes omitted the road name, just showing the route number. Two notable exceptions were tourist routes (like Great Alpine Rd), and Sunraysia Highway as you can see here.

Does anyone know the reason for this? It's not like it's a few that may have been by mistake, it seems like every sign on the road has the road name.

[barbs]

I believe the reasoning at the time from Vicroads was that it was a major freight route