Also note the 2019 Air they've got has a smaller battery again (49.9Whr).
The battery life gains in Macbook Air might come from the different series of processors used, rather than from the battery itself:
> The MacBook Air has Core i5 and i7 processor options, but they're part of Intel's "Y" series of CPUs, intended for thin laptops. They generate less heat and use less power, so you get longer battery life. The flip side is they're not as fast as a standard laptop with a "U" series processor.