Sorry but that just isn't right. The battery you listed is an just an NMC battery , the listing pages are just lazy and don't list it. There isn't just a plain lithium ion cell. Also lithium polymer just means that a polymer electrolyte is used instead of a liquid electrolyte.

https://en.wikipedia.org/wiki/Lithium-ion_battery

That's pedantic. They're sold that way by the truck load and anybody that buys them for DIY purposes knows that this is how they are designated. People are buying based on the working voltage nominally 3.6V, Lithium Ion chemistry, battery capacity, form factor. Not on the internal details of the battery, which are not normally listed in sales documentation on consumer oriented outlets anyway.

Yes, you can go into the details of the exact chemistry, the packaging, the manufacturers specs and so on but for bulk DIY purposes this is the reality. The detailed chemistry obviously has some implications for safety but because you will have no idea what is in a pack unless you open it (and plenty of times the cells are unmarked) you just have to assume the worst. That's the safest.

> People are buying based on the working voltage nominally 3.6V, Lithium Ion chemistry, battery capacity, form factor. Not on the internal details of the battery, which are not normally listed in sales documentation on consumer oriented outlets anyway.

Lithium Ion chemistry is the internal details of the battery. Which denotes the type of lithium ion battery, there is no generic lithium ion battery. It will fall under a certain category (Ex LFP, NMC, NCA).

The same battery you linked on other websites is called out as NMC: https://voltaplex.com/sony-vtc6-18650-battery-us18650vtc6

Sure you can go buy unmarked cells on ebay but any reputable website should list the battery chemistry on their website or have a link to the datasheet. It is no different than buying any other electronic component.

I've refurbished many packs and built my own, for cameras, e-bikes and laptops. I've yet to find anybody other than myself to be interested in the exact chemistry of the batteries involved. What they're interested in at the highest level is whether it works, and second to that how much it will cost them. I'd be happy to bet that most people that use these batteries would not be able to figure out what exact composition a cell has nor would they care.

It is very clear to me that there is a vast gulf between DIY and professional application, and for the latter I'm 100% sure that everybody there would be able (and should be able) to make the distinction. The number of hobbyists that can do so is going to be very low.

For maximum cringe, have a look at this youtube video and spot the potential problems:

https://www.youtube.com/watch?v=DAoCK3QNLng

And that's one of the very best.