"My original question is though: RPi 4B is much faster according to many
benchmarks, but why does Moodle Benchmark say the opposite?" - I finally got a chance to do some testing, and came up with slightly different results than what you have at http://www.syndrega.ch/blog/. I only tested RPi3B, and RPi 4B.
My RPi 3B for the most part, mimicked the scores shown for yours, except for the last two items, guest account and user account which were noticeably slower, so that the best overall score for four runs, was 1.742s.
The best of four runs of my RPi 4 without heatsinks was about the same as yours at 1.631s. With three low profile heatsinks on the cpu, memory, and USB3.0 controller, my best run was actually slower at 1.638s. When I also added a fan above the cpu heatsink, my best run for the RPi 4 came in at 1.611s. Eventually, I hope to test with bigger heatsinks that are not compatible with fans, as shown in one of my other posts.
I also tested a RPi 3B using an older version of Raspbian, Apache 2, PHP 7.0.33 and PostgreSQL 9.6.13 and got MUCH WORSE results, with the best being 4.71s. The biggest performance hits were cpu and the two database scores.
I will say that the RPi 4 with the USB 3.0 Gigabit Ethernet does seem to give much better overall Moodlebox performance than the RPi 3 with it's slower 100 Base Ehternet.