Does the Ecolink Tilt Sensor model TILT-ZWAVE2.5-ECO require a custom DTH or just the basic ST integration to use on a garage door?
I use the stock ST device handler → Z-Wave Door/Window Sensor (note: I have an older z-wave model not z-wave plus)
why does it seem strange?
In reading the instructions it talked about configuration and associations groups and how to configure but there were no options for that.
I guess that’s what I get for reading instructions! 
I have the 2.5 (zwave plus) and that looks right.
also, have it for ring alarm.
Zwave direct Association is an optional feature available with that device, but most people using smartthings would not use it As you can achieve the same outcome with the regular automations. 