I know DL requires all planes to be tugged in and out to taxiway at LAX due to tight alleyways. The gates just are so tightly spaced for the size aircraft using them.
As for the late arrival, until the plane is fully parked at the gate, it hasn't arrived. Thus you could be 5 feet away and have to wait past arrival time and thus even though 30 minutes early landing you're now a late arrival.