SB Nation did a comparison of HS 40's vs. NFL combine 40's a few years ago, and the overwhelming lower times between HS and NFL clocked times appears to be a recognized part of the recruiting game.
http://www.sbnation.com/college-foot...ard-dash-times
However, I did find a mention in the Pensacola News Journal which named Damond to their First Team Offense for 2015, and the 4.28 is attributed to a Florida camp-
"WR – Damond Johnson, West Florida
The speedster ran a 4.28 40-yard-dash at the University of Florida over the summer and lived up to the hype this season. Johnson snagged 38 passes for 761 yards and 12 TDs this season, leading West Florida into the postseason."
http://www.pnj.com/story/sports/high...team/77889688/