Reverse Polarity "Protection" is not the same as "Tolerant"
The TP variant that has the protection modules are NOT "Polarity" protected. The only reason it works at low voltage is because of the VG voltage required to turn on the dual mosfets. However, if you were to leave that weak cell plugged in, it would eventually burn out the chips.
You can get a better view and explanation of this particular module on Julians video on this particular module. He discusses a bit of the datasheet at the beginning of the video. Note, the datasheet does NOT say "Reverse PolarityProtection", but mentions "Over-Charge" or "Over-Discharge" protection.
As you said:
I would have a lot of dead tp4056 if it didn't have reverse polarity protection. Protection is limited to 3A though, so if you do it with a deadish cell it should be fine, a cell with a reasonable charge could definitely do more than 3A burst.
If it was reverse "polarity" protected, it would be able to handle a better amp, and would be able to handle a "reasonable charged" cell. If it can only handle a "deadish" cell, then it's not reverse polarity protected.
Also: If you jump to time index 11min44secs of the video, Julian specifically talks about the protection portion of the board.
"A new board with an unprotected cell is equivalent to the old board with a protected cell because the protected cell has those battery protection components inside it so they don't need to be on the charger board. In the case of the bottom board, the protection components are on the board so they don't have to be in the cell."
I have never heard of a battery protection circuit that is on the cell (aka CID) that is reverse polarity.
If you want to get the most out of your TP4056 charging modules, make sure you do not plug them in backwards. Each time you stress the chips, you weaken their ability to function properly. Sure they are cheap modules, but why waste money on replacement parts from laziness. The 18650's are easily recognizable as which end is positive and which is negative. The positive has a button like raised end just like "any" other common battery. And they even have a crease around the positive end as well. How can you not see that? Even a blind person could put these cells in a charger the correct way.
Ok, that was my rant for the week. Please continue with your regularly scheduled charging/building