I would not use this site as it overestimates fees way too much. Right now it's estimating 10 sat/byte needed for the next block, but 1 sat/byte is going through at the same speed (I sent a 1 sat/byte transaction 5 minutes ago, and it confirmed next block)
Wow, you are absolutely right. It's completely obvious as well, yet I've never noticed before. Looks like it is grouping 1-5 in with 6-10, 11-15 in with 16-20, and so forth.
Thanks for pointing that out.