To be clear, Jonny used a Boss RV-3 pedal back when he still toured with a Roland RE-201 Space Echo unit. Jonny stopped touring with the RE-201 in 2010, but he didn’t start touring with a Boss RV-5 pedal until 2016.
As for the signal chain, it’s just convenience. Jonny kept his Roland RE-201 Space Echo on a stand beside his pedalboards, and he didn’t want to run extra cables. It was easier to send the output of the pedalboard to the Space Echo.
Once Jonny started using a Boss RE-20 Space Echo pedal, he placed it before his reverb pedal.
But for what it’s worth, there isn’t a huge difference when placing reverb before or after delay. It’s noticeable, but not dramatic like putting delay before and after distortion.
Jonny’s pedalboard from Radiohead’s appearance on Austin City Limits on March 6, 2012. His “Vox” signal chain (selected by his Boss LS-2) features a Boss OD3 overdrive, Boss RE20 delay, Boss RV3 reverb, Akai Headrush E2 looper, and Boss FV300H volume pedal (resting beside the board and used only for Feral). The modulation pedals on the other pedalboard are connected before the LS-2, so they can be used with either of his amps.