Abilene Municipal Airport problem reports

Since last year, hundreds of airports like K78 have had another K added to the front of the ID. All of these IDs contain numbers (1N1, I69, etc.). The convention used to be that only airports listed with ICAO began with the letter K; all other small local airports were 3 numbers/letters only. Did these airports suddenly decide to all register with ICAO? If not, why was the leading K added, and will it be removed to conform to what I understand to be international standards? Or did I miss something? Abilene is still K78 with airnav https://www.airnav.com/airport/k78