No need to get me started with the lack of documentation around ubus, procd, netfid and all the rest. There aren't even decent technical descriptions of how they work. Most of what's on the wiki is wildly outdated, outright wrong, or both. The answer seems to be "read the source code" if you don't like how LuCI configures your system.
On the specific question, [Solved] Dnsmasq resolv.conf inconsitent might help