Thats very true, a clone is an exact look alike but in the world of FFVII a Sephiroth clone is someone seen as being as strong and having abilities equal to that of Sephiroth. Dont believe me? Then open your copy of FFVII and start playing. When Clouds past is uncovered in the lifestream they hold a meeting on the Highwind. He then says that the cloning process was just spraying normal members of soldier with Mako. Like I said before, and again before that. Its a misunderstanding of what exactly is a clone. While you may be correct on what a clone is in real life this is Final Fantasy. The sephiroth clones were kids injected with jenova cells? No, as far as the FF storyine was concerned Sephiroth was the only one who received Jenova cells as a child and if you pay attention Im pretty sure he received them through his mother while he was in the womb. This was a private experimentation on Hojos behalf because ..well he was crazy. Trust me there wasnt a bunch of pregnant woman being injected with jenova cells. The whole process of spraying every member of soldier with Mako was to make them Sephiroth clones. Yes thats right, what Im saying is Shinra wanted to breed an army of Sephirots.
Are you suprised? How exactly did you work out the Seph clones were all kids? True thats how Sephiroth was created but Shinra used a different method. Which pretty much didnt work except for the black cloaked men and they werent between five and seven years old when they received the mako. The clones you saw in the game were Soldiers who were all injected with Mako as adults. They were not Nibelheim townsfolk because they were majority (or all) killed in the fire.
Again, check the part in the game on the highwind, after the lifestream. Cloud says that the cloning process was just spraying soldiers with mako. In different levels of mako, having different effects.