Is this a new website or an updated version of the bitcoinfeesearn (cmiiw) site?
It looks like the calculation is still not that good since you can send 4 sats/vbyte just fine if you take a look at the mempool. If you follow the suggestion of that site you'd overpay close to 10 times.
https://mempool.space/Its a separate website not the shitty bitcoinfeesearn but this website also doesn't look good?!

Its a decent website and I follow most of the time with the recommended fee in this site but I think its time to go with something better.
https://mempool.space/ this site shows the transactions stats in real time?