>>514677147 (OP)
It's because they changed the rating system to make it more difficult for a tornado to reach the criteria for being classified as EF5. Specifically, you need homes that are built to a specific standard, which get completely swept off of their foundations. A lot of times, there will be houses that get completely wiped away, but the houses will be deemed too structurally weak for it to count as EF5 damage. The EF scale is based on damage indicators as a proxy for wind speed estimates, rather than direct measurements of wind speeds.