"Power bank cells are mainly divided into 18650 cells and polymer cells. The most common one on the market is 18650 lithium-ion batteries, with a market share of 70%."

https://www.benzoenergy.com/blog/post/type-of-cells-used-for...

Looks like the article you've shared is from 2019 (at the bottom of their page?).

Things changed a lot since then. Most power banks these days use just lipo pouches.