I think you're missing the point. The signs do not need to state merge in turn, it's what you should do by default.
I'm not disputing the merits of merge in turn. I think for the majority of drivers in this video queuing was a reasonable course of action, perhaps not the best but given the lack of signs it's reasonable to expect.
However, undertaking a long queue of traffic at speed under the guise of practicising merge in turn is not reasonable. The queing traffic is virtually standstill with none or very little space to merge. So you've no realistic chance of merging anymore and you've irritated a large group of drivers as well as compounding the problem of the queue.
The 'get in the correct lane for your vehicle' that you keep highlighing is not really relevant to the discussion as it's more for heavy/high vehicles.
Temporary lane closures apply to all vehicles.