You have gotten enough contra for this as this has nothing to do with science but teaching (and has long been tested), but one misconception I have not seen add

You have gotten enough contra for this as this has nothing to do with science but teaching (and has long been tested), but one misconception I have not seen addressed yet is the fact that although there are some differences between cells, those are minimal from a genome stand point (a few changed letters of 10^9 in total). If you have two books with the same text and one has ten commas more, randomly distributed through the book, you would probably also call them identical(or not even notice) although they are not. As a further note, while we can sequence the genome of cell bulks since about 2004, sequencing of single cell sequencing came up in the last ten years (with an accuracy of about 99.99%, so many random mistakes add up to a much higher degree of variation as is observed here), so if you did not went to science class less than ten years ago (with a teacher trained in the same time frame), your argument does not really make sense.