You forgot to mentioned what router model you have. I had to look at your previous posts to find what eventually the model is.
The router with NVRAM issue is RT-AC
68U. Your router is RT-AC
86U. Do you see better now what
@dave14305 was talking about?
We had a very recent (from today) conversation about this
here, and in
3 more places in last 10 days only. It's one of the workarounds for people having AiMesh issues when the main router is running Asuswrt-Merlin. For your router in AP Mode - it doesn't matter what firmware you use. There is no routing on an AP (it's just a wired-to-wireless bridge + switch) and there is nothing much to use from extra Asuswrt-Merlin features.