That's a different scenario. We will have agreed on a price in advance, so it is clear what you sent was a mistake.
If I pay 100 sats/vbyte in fees, is that clearly a mistake? What about 200? 500? The
last block contained two transactions paying over 1,000 sats/vbyte in fees, when 40 sats/vbyte would have been sufficient. Should the miner refund those transactions? Or indeed, should they refund every transaction which paid more than what was necessary? What's stopping me from making all my transactions pay 1,000 sats/vbyte and then demand that the miner return my fee?
These are excuses and you know it. You ignored the parts where I mentioned: "If
you know that someone paid you too much in error, and it's
practical and possible to refund them". No one is talking about anyone demanding a refund, but whether it would be a moral thing to do from the recipient's perspective.
Just because it's judgmental of what the "refundable" amount would be, it doesn't mean it's the right thing to keep any amount sent in error (even if you have a legal right to do so).
Somehow nobody in this thread had any trouble recognising that 20btc was not a normal fee and it was likely sent in error.
If you send all your coins to the wrong address, no one can get them back for you.
Recipient could. If I sent all my bitcoins to your address by some weird accident, I'd like to think you would return them. Not because you have to, but because it's the right thing to do.
I don't see why we should expect any different if you pay too much in fees. You might get lucky and the miner in question might be feeling generous, but you definitely shouldn't work on the assumption that they will refund your fee nor that you would have any legal recourse in such a situation.
Nobody is saying anything about any "expectations" or about introducing any rules that miners must refund such fees.
As for legal recourse - you don't know that. I could easily imagine miner being ordered to return it in some jurisdictions.