https://wccftech.com/13-inch-2018-macbook-pro-full-speed-thunderbolt-3-ports/

The latest 2018 MacBook Pro models start from $1,799 (you can click on the link below to learn more about the pricing comparisons) and all variants feature the Touch Bar. The 13-inch models belonging to the 2017 and 2016 lineup that also featured a Touch Bar came with four Thunderbolt 3 ports, but they were not running at full speeds. Apple has rectified this little limitation with the latest 13-inch 2018 MacBook Pro family as they now feature four Thunderbolt 3 ports running at full speed.

Since both notebook computers now come with an Intel 8th-generation Core processors, they are able to support 16 PCIe lanes. This is sufficient for providing complete bandwidth to the 40Gb/s Thunderbolt 3 ports on all notebook models, according to info from MacRumors. Previously, the 2016 and 2017 MacBook Pro models came with a total of 12 PCIe lanes, which means that the Thunderbolt 3 ports could not run at their maximum capabilities.