As nabatean, I had to build a wooden wall (2nd tier wall) in Rekem to get the Arabain tribes to settle (reform). (More exactly, my capital must have a wooden palissade or higher, and I need to have 3 cities with a wooden wall, so I decided that my capital would be one of the three cities)
In early game, I upgraded pastoralism to its 2nd tier, then I converted the camp to a settlement. But, instead of getting a same-tier wall, I got a palissade, even though I have about 3500 inhabitants.
So, tu upgrade it to a wooden wall, I have had to cheat and add population to 6000 to build the wooden wall. Now I must wait 12 000 instead of 6000 for the stone wall, etc.
I guess I shouldn't have upgraded pastoralism.
But I think there's a problem in the conversion process.