Here I will disagree. The user in this post bought a device they claim was suggested on OpenWrt (WR802N), yet it only has a community supported version available and relatively little documented on the device. I do not think they are reading well.
The existing message does not stand out well. Let's at least make it bold, but I think the message can be stronger and included in other places too. As @slh pointed out it is the novice who gets into trouble. Anyone who can build LEDE probably understand the issue and how to solve it.
I do not know what the feasibility is of reworking the default images on these to include extroot configured for devices with 4mb and USB. Would this not go a long way to addressing the issue for both Trunk and Release? If I understand this, one pretty much would just need to plugin a properly formatted drive and go.