LHR-SOF would just fall into Zone 3, so 12 points for a return - currently it's 10. So Zone 4 will become worse value for Platinum, but ever so slightly better for OW Sapphire. The better value is in groups 4 to 6.

A SOF return gets you 8.5% to Platinum, 17% to Gold. BA would have been 10.6% to OWE, 25% to OWS.