Good observation. At least 2 of them being run without narrow wide chainrings it looks like. Before I started riding an e bike, I would prefer to take off the derailleur, run a big narrow wide, then just shift it down to the granny by hand if I needed it when I'm getting tired or on a really steep climb. But to each their own. Front derailleurs are less problematic and dangerous than rear derailleurs.
Some look like older(small) models that have been repurposed as junior bikes, probably something to do with the lack of other options at reasonable prices especially given they will grow out of them fairly quickly. They are possibly a bit of a spare parts bin build and might not want to go 1x on a 11-36 cassette!
Sid Hunter's Specialized Stumpjumper appears to be the 2013, which had a significant paint defect. Basically any amount of sunshine/uv light would fade that orange to a gross yellow. It’s unsurprising that in the UK it’s still perfect almost 10 years later.
Poor kid on the GT (the brand that he rode to take the overall junior WC DH on) who put in the 4th fastest time of the day (and 2 out of the 3 of the riders who beat him were on ebikes).