Actually it is worse than that. There are many values for ohms/1000 feet for any gauge wire especially when it comes to stranded wire. I once measured a bunch and got these results: [Link: audiosciencereview.com]




As you see the DCR (in milliohm) changes a ton.  Here is the relative graph to Belden:



Your larger point is definitely correct.  We had a Savant thermostat which would reset once a day or two.  Turned out the AC run from the HVAC had too much voltage drop causing it to do that (Savant support instead sent our tech on a wild goose chase telling him the voltage was too high, needed new firmware, hardware, etc.).  Thicker wire solved that even though the run was not that long.