He doesn't have any military appointments as far as I'm aware. And he is not a working royal - consider him to be the same level as HRHs Princesses Beatrice and Eugenie. Each of them might do a one-off here and there representing the Queen and appear in the Court Circular for that.
So, Harry losing any honorary military appointments since he is no longer a working royal is in keeping with the way other non-working royals have been treated. And he and Meghan still have their HRHs, they have just been told they can't use them on their commercial projects. I'm not sure whether or not Prince or Princess Michael have used their HRH on any of their commercial activities (she has written quite a few books which have been well-received).
FWIW, Wikipedia shows Prince Michael as having a number of honorary military appointments. Maybe those are different somehow? He's been pictured in uniforms fairly frequently.
United Kingdom Honorary Commodore, Royal Naval Reserve (1 April 1994 – 2004)[48]
United Kingdom Honorary Rear Admiral, Royal Naval Reserve (2004–2015)[49]
United Kingdom Honorary Vice Admiral, Royal Naval Reserve (9 March 2015 – present)[50]
United Kingdom Honorary Auxiliary Commodore, Royal Naval Auxiliary Service (1990)[51]
United Kingdom Commodore-in-Chief, Maritime Reserves (2006–present)
United Kingdom Honorary Colonel, British Army (10 November 2010 – present)
United Kingdom Senior Colonel, The King's Royal Hussars[52]
United Kingdom Regimental Colonel, Honourable Artillery Company (2009–2012)[10]
United Kingdom Royal Honorary Colonel, Honourable Artillery Company (31 January 2012 – present).[10] (member since 1981)
United Kingdom Honorary Air Commodore of RAF Benson (27 June 2002 – 2012)[53]
United Kingdom Honorary Air Marshal of RAF Benson (1 March 2012 – present)[54][55]
The Wayback Machine features his private webpage as HRH Prince Michael of Kent with a subsidiary page of the website describing his business interests:
web.archive.org
I'm just not really seeing the difference.