He doesn't want to be cloned, which basically sounds like a sci-fi movie plot where he gets replaced with a flash clone. He's probably being more paranoid than necessary and looks more foolish than necessary for someone who is in charge of a country.
There are other more realistic concerns like surveillance by DNA sampling and framing by DNA planting. Genetically specific poison could be also possibility.
In addition there are probably more valid reasons for heads of state not to have DNA available to a possible future adversary. A more reasonable fear would be these two from
+You may be discriminated against in the future. In the United States, health insurers and workplaces are not allowed to discriminate based on DNA. But the law does not apply to life insurance or disability insurance. Who knows in your case, where you live? Some day you could be compelled to share genetic information with your own insurer.
+Racists are weaponizing the results. White nationalists have flocked to commercial DNA companies to vie for the highest race-purity points on extremist websites.
