Framing for 1970s sizes
For a new install, that matters because most of the openings a homeowner here is dealing with were framed for the standard door sizes and hardware of the early 1970s, not today's. If your house dates from that era, the rough opening may be close to code but the header, the track clearance, and the spring mount are not going to match a 2024 door pulled straight out of the box.