The ruling is 6-3 ONLY on whether to uphold the particular Miss law at issue. One whether to overturn Roe it was 5-4, with Roberts voting with the left to uphold both the Miss law AND Roe.
“Over the protests of Chief Justice John Roberts, who voted to uphold Missisippi’s 15-week abortion ban but not to overturn Roe, the status quo of the past 49 years is gone. (The three liberal justices dissented in full.)” https://fivethirtyeight.com/features/the-supreme-courts-argument-for-overturning-roe-v-wade/
Not so significant, as it will be known as a 6-3 ruling.