This is true for sure that pressure is not affected by distance if there is a Trade Route. However i was under impression that Traderoute just equilize pressure between cities, so that if cityA has +25 and cityB has +5 than Traderoute between them will make cityB +25 and cityA will remain the same.If you have a trade route, the pressure is not determined by distance
Though i don't know if there were any changes to that over the past months. Changelogs do not have any changes but from time to time a brownie elf steals some entries from the changelogs...