Technically they are not relevant to the flat earth. They only seem relevant when you try to impose the false model into the flat earth reality.
Applying parts from one model to a different one, and then dismissing it because wouldn't work.
This is foolish to do no matter what topic you are discussing. He must first learn why this simple logic is ridiculous before he could ever grasp what we are talking about.
Another factor is believing that a rover is on mars, therefore mars must be an object similar to the earth. This keeps him locked into a mentality where these parts he believes operates his universe are fact, and must be accounted for in any alternative models.
Now he can dismiss the extreme similarity between mars and earth because he thinks they are both similar objects formed in the same universe. This lie ensnares
A rational person must accept that the hills and formations on Mars, that some astute individuals were able to locate on earth,
expose the hoax entirely. A rational person understands how impossible that would be for the same exact pieces of land to appear on two planets within the same "system".
So he must believe the mars photos supplied are fake in these instances. All NASA has to do to cover their tracks is delete them:
https://www.reuters.com/article/us-...-got-erased-nasa-admits-idUSTRE56F5MK20090716
So you have someone that can't think outside of his current understanding or accurately consider other possibilities, and when confronted with undeniable evidence it either isn't understood or it's dismissed.
There is nothing we can do for him. He has so much faith in the authority that presents his model, and the half-truths have completely overtaken his reality and mental faculties from being able to see outside of it. "Oh all planets are similar, so they are going to look like earth". "Am I going to believe internet conspiracy theorists or the government I help fund billions of dollars to a year?"
Now to explain the evidence or logic I posted is false, some people will then give themselves and incredible pat on the back for the efforts it takes them to remain locked into their lie, because these are logical matters and we simply can't look at physical evidence or consider people are lying or fooling us with the tools available to everyone common citizen.