What they're saying is that English doesn't have 21 consonant sounds and 5 vowel sounds, which is 100% accurate. English has 21 letters which we identify as co

What they're saying is that English doesn't have 21 consonant sounds and 5 vowel sounds, which is 100% accurate. English has 21 letters which we identify as consonants and 5 letters which we identify as vowels, which are used to write ~24 consonants (depending on accent, but generally clustered around there) and a large number of vowels that is impossible to neatly catalog because it varies widely by accent—it's somewhere in the neighborhood of 14-25, depending on accent.