Have you ever looked closely at those NBA website numbers? I'm not barking at you about it - it's not your doing. The first time I saw that I thought it was going to be great, but it doesn't tell you . You can't compare apples to apples at all, because of what they're measuring and how.
That NBA website shows offensive and defensive "average speed" (whatever the that means). Last year, it says the fastest on defense were: Cunningham, Poeltl, and... Motiejunas? And for overall "average speed", it shows Motiejunas as being faster than DeRozan and just a hair slower than Lonnie Walker. That alone should tell you that it's meaningless. White was considerably faster in the 3/4 sprint at their respective combines, when they were both young. Now Cun has been around for 10 years or so - there's no way he's faster than White.
White's sprint time would make him one of the fastest in any combine in the last 10 years (maybe longer). He would have been the fastest in 3 or 4 combines in that timespan. And of the few guys who were faster, probably half never made it in the NBA. He's quick enough to blow past a majority of defenders. If he's improved skills and confidence in the offseason, it's going to be hard to keep him off the floor.