Technically, they're (or should be) referring to "txouts" or "outputs". An address with a large balance could still be unspendable if it is composed of many small outputs.

A single address can be the recipient of multiple payments (outputs) and a transaction spends those outputs. Since each output must be referenced in a transaction, each output takes up some space and fees are calculated based on the size of the transaction in bytes, not its value in BTC. This diagram I made a few years ago might help visualise: https://github.com/olalonde/bitcoin-notes/blob/master/svg/tr...