I think they are trying to be clear to walkers and campers that the campsite and trail are closed.
My understanding is that the campsite is to be closed permanently, but the trail will eventually form part of the Grampians Peak Trail, as shown on this recent brochure:
In the meantime, there is no indication that the area is closed to climbing. Climbers should be free to access the cliff. The most sensible and lowest impact option for that would be to use the existing trail as an access trail, being mindful of not interfering with any works along the way or worsening any erosion issues. There is no other way of accessing the cliff unless you bush-bash.
I suspect that if you asked Parks directly as an individual they would say that the trail is closed and shouldn't be used. VCC Access/Cliffcare probably has a better chance of coming to an understanding on climbers access based on the issues associated with the track closure and when/where work will be done. It has parallels with use of the Giants Staircase and the approach trail to Mt Rosea as a climbing access trail, except that at some stage they are likely to be doing construction work and genuinely won't want people around.
So, I reckon the definitive answer is that that trail is closed - bush-bash your own way in (maybe 50 cm off the track?). The practical answer is deliberately obtuse.