From the first one:

> To mitigate these issues, external contacts may typically include a corrosion-resistant coating to the exposed exterior surface… Although temporarily effective, such coatings are subject to frictional wear and may become less effective over the life of a device.

Frictional wear is not a huge problem in practice.

There’re billions of devices with built-in batteries in the world. I’ve been carrying a cell phone, and later sometimes other electronics, since 1999. Never encounter such issues.

Most manufacturers use gold plating, and they advertise reliability for 10000 mating cycles:

https://gct.co/usb-connector https://www.gradconn.com/Products/MicroUSB https://www.molex.com/molex/products/datasheet.jsp?part=acti...