"It has been a while since Sony released a pair of WF-1000XM earbuds, although the company has only launched one pair so far."
Incorrect, the WF-1000XM3 is Sony's second pair of WF-1000X series earphones, which would make an M4 the third model to launch.
Sony released the original WF-(Wire Free) 1000X buds in 2017. The M3 (Mark 3) came in 2019. For anyone wondering, they skipped the M2 naming convention altogether, never releasing a product with the WF-1000XM2 designation, because they wanted the product launch of their new earphones to correspond with the naming convention of their current over-the-head sister product at the time, the WH-1000XM3 (Wireless Headband 1000X Mark 3) which were released in 2018, so the buds released in 2019 that you reference in your article became the WF-1000XM3 to create naming symmetry between the WH and WF series. Even though it ends in "M3", indicating Mark3, it was actually only the second model in the WF-1000X lineup.
So there's some insider info that nobody asked for...