[prevent]

What do they exactly (precisely) mean by this:

He was insisting that I ship the laptop with FedEx ground shipping because it has tracking. I assume that he's still insistent on that.

However, FedEx will not accept goods with leaking batteries, correct?

wrong.

There are several regulations surrounding the safe transport of lithium batteries. Remember: all types of lithium batteries are considered Dangerous Goods and must be handled and labeled properly. The type of lithium battery, quantity, electric capacity, charge and how they're packed — whether they're contained within equipment, shipped with equipment or all alone — are all determining factors in how to pack and label lithium battery shipments. Whether it be by air, ocean, rail or truck, there are many regulations in place and it can be difficult to know how to properly pack, label and ship these batteries.

been had that pulled on me before.

from what I remember when I SE'd my switch, they said just bring it into fedex because they can package it there for you. (If it's a "dangerous goods") ALSO USPS does it too if you're wondering.
https://www.fedex.com/en-us/service-guid...rials.html