No. Does his service suddenly mean he's incapable of lies and fabricating stories?
It does not. However, Kelly is not the only person who worked with and was close to Trump during that time that has spoken against him for a variety of reasons. These folks include:
VP Mike Pence, attorney general
Bill Barr; secretaries of defense,
James Mattis,
Mark Esper; chairman of the joint chiefs, retired
Gen. Mark Milley; secretary of state,
Rex Tillerson; ambassador to the United Nations,
Nikki Haley; presidential transition vice-chairman,
Chris Christie; national security adviser,
HR McMaster; national security adviser,
John Bolton; chief of staff,
Mick Mulvaney; communications directors,
Anthony Scaramucci,
Stephanie Grisham; secretary of education,
Betsy DeVos; secretary of the Navy,
Richard Spencer; homeland security adviser,
Tom Bossert; White House lawyer,
Ty Cobb; director of strategic communications,
Alyssa Farah Griffin; deputy press secretary,
Sarah Matthews; chief of staff’s aide,
Cassidy Hutchinson; etc.