135 CFM is pretty weak. I wouldn’t think a 40V blower would have numbers that low.
Voltage alone has no correlation to performance; overall power and design does. There are 18V cordless saws that will outperform a 120V corded saw, y’know. How and where they measure the maximum air speed differs from brand to brand too.
In this instance, it’s GW’s entry model. They have higher performing ones, but they want more $$$ for those.
(Note that I am not staff. I just volunteer to help out on the forums.)