"Scientific knowledge is always in a state of flux". This is not true, as far as i know, most scientific knowledge is absolute truth that you can not challenge. I wished the shaykh gave examples about flux in science. What i know is that the main miracle of Quran was its utmost eloquence for Arabs who were at their climax of lang-uage mastery. Since non-muslims now do not speak Arabic but the elite of them speaks science lang-uage, therefore, scientific miracles of the Quran are suitable more than ever. If the "salaf" did not go this way, it's does not necessarily mean search for scientific miracles in the Qur'an is forbidden, particularly given that "Salaf" did not disprove it, apparently they found other ways to invite people to Islam. Since we are in the era of science why scientific miracles in Qu'ran are not suitable to invite non muslims.
Some verses of Quran are quite clear. Here an example of verse that can be literally interpreted and therefore unravel a scientific miracle of Quran. From surat el-ruum: “The Romans have been defeated in the lowest land, but after their defeat they will soon be victorious. Within three to nine years. The decision of the matter, before and after, is with Allah.” (Quran 30:2-4). How do you interpret "lowest land"? it means what it means, a place where the battle happened, and science found it to be the lowest elevated place, below sea level, on earth. On contrary, the Quran should lead the scientific discovery such us for the example above.