Well, only limited information available.
I donˋt wanˋt to blame anyone, but experience shows, that it is quite common ( illegal ) practise within the light fixed wing world to fly their „own IFR approaches“ operating under VMC rules....
Was scared more than once from TCAS, warning me from traffic close above, while operating in a helicopter at 800 feet or less above ground, just below cloud....
Always close to smal airfields....