Genetic barcoding is a molecular technique to identify different species based on their DNA sequence. Genes that encode ribosomal RNA $($i$.$e$.,$ rRNA$)$ are often used as DNA barcoding markers because they exhibit multiple aspects that make them suitable for DNA barcoding across the different domains of life. However, there is one feature about rRNA$-$encoding genes that is unusual compared the rest of the genome, complicating the usage of these genes for DNA barcoding. Which of the following aspects is NOT true about rRNA$-$encoding genes and their suitability for DNA barcoding?

rRNA$-$encoding genes occur in high$-$copy numbers in a genome and are, thus, easy to extract in the laboratory

rRNA$-$encoding genes exhibits the accumulation of random mutations and, thus, accumulate nucleotide changes at the same rate as any other region of the genome

rRNA$-$encoding genes are present in virtually all prokaryotic and eukaryotic organisms, albeit with slightly different nucleotide sequences

rRNA$-$encoding genes are highly conserved and, thus, quite similar even across distantly related organisms