Looping in Carlos from the Cloudflare team who might have more thoughts.
Cool to hear you're looking at the Cloudflare data, feel free to share any interesting insights. Each row is a
speed.cloudflare.com single speed test result. If I understand your question correctly, I believe the difference in number of rows is simply due to the amount of users taking each test. NDT's integration in Google Search means it tends to get more traffic than some other tests (~4m per day globally).
Hope this helps, let us know if we can answer anything else!