Looks like SeatGuru always links to the 75S seatmap for any flights flown by a 757-200. In other words, it's a bug. Sorry OP, but you will be on a 75D model with standard domestic FC seats (as can be confirmed on delta.com).
https://www.seatguru.com/airlines/De...aii_75H_v2.php
DL does use the 75S on some non-D1 routes (like JFK-SEA), but it doesn't have any doing LAX-MCO.