That is because 6 is a priomorial. For any primorial p', k*p' +/- 1 will result in a number relatively prime to p', some of which are absolute primes.

The key to understanding primes is in relative primes and reduced residue sets. All patterns in (higher) primes (absolute) are generated by the members of RRS of primes smaller. This includes the clusters, such as twins, triple, quadruple, ..., primes. RRSs also hint [imo] at intimate connection between complex numbers and primes.

https://en.wikipedia.org/wiki/Primorial

https://en.wikipedia.org/wiki/Coprime_integers

https://en.wikipedia.org/wiki/Reduced_residue_system

https://en.wikipedia.org/wiki/Root_of_unity