For "Compatible" here probably is intended device supports all the features the map offers and it's firmware is designed for displaying that kind of map.
Series 1xxx sw is designed till now for NT maps and NT is map 1xxx receive from Garmin server at update session, btw people often says NTU works fine. I'm not so sure if search is perfectly working with NTU in 1xxx series.
I tested once in a 1200 and I had to remove it and replace with NT coz some addresses were unreachable, but it was long time ago.