It's been a few years now but I used to work on research on this particular alternative receptor.
To handwave and simplify a bit CCR5 is the dominant pathway for the virus to spread in a healthy patient. HIV tends to mutate in patients from attaching to CCR5 (called phenotype R5) to CXCR4 (called X4) once the immune system is weaker. Patients with the X4 are not as infectious as a healthy immune system can fend it off.
So CCR5 is more or less the only pathway for the virus to infect a healthy host, as far as I can remember.
To handwave and simplify a bit CCR5 is the dominant pathway for the virus to spread in a healthy patient. HIV tends to mutate in patients from attaching to CCR5 (called phenotype R5) to CXCR4 (called X4) once the immune system is weaker. Patients with the X4 are not as infectious as a healthy immune system can fend it off.
So CCR5 is more or less the only pathway for the virus to infect a healthy host, as far as I can remember.