Ready Action vs Extra Attack

The Concern

A creature with Extra Attack uses the Ready action to swing at an enemy when they close in. Do they attack only once, or multiple times?

Details

RAW: "...you can attack twice, instead of once, whenever you take the Attack action on your turn."

Ruling

As RAW - ready allows you to act outside your own turn using your reaction, so it's not the Attack action (it's downstream of the Ready action). Therefore, only a single attack can be made on a Readied attack.