I didn't spot an argument. What I saw was kicking the can further down the road. SO, OK, FD lets people without Horizons do atmospheric flight. His target flees to a planet. He follows. His target sees that he is followed, so drops to the surface. At this point the apparently game now stops the OP from following. If is clearly unfair. FD should let people who did not buy Horizons land on planets, too, otherwise the game is and their targets can escape, and that is not fair.
... but, wait, my target has now jumped into his buggy. But I did not buy Horizons and so do not have a buggy. Clearly the game is and I am being treated unfairly. Obviously the only fair thing to do is to let those that have not bought Horizons have full access to Horizons, otherwise it is and not fair.
Did I get the gist of it?
Really, there are lots of things you can criticise FD for. I do it regularly. But this is laughable as a complaint when today, with or without Horizons, your target can escape through several techniques, from emergency drop out of SC followed by a logout or change to solo to logoffski to many others. Live with it.