Our jetways don't have any special "auto attach" feature, since there's no such thing. A jetway either works or doesn't, under a certain combination of airplane doors, parking position and jetway placement in the scenery.
If you noticed they seems to work more often than other sceneries jetways, it might just be sure to the fact they are better modeled, so they have more chances to "solve" with more airplanes from more parking positions.
Now, why they attach "automatically", it's a completely different matter and it might caused by:
- The airplane triggering the jetway itself, with some custom function to handle jetways
- The AI Copilot in MSFS doing that as part of his tasks.