Install it or no ?

I have the legacy API (old one). I’m really confused. You write about your plugin here https://www.ads-software.com/plugins/woocommerce-legacy-rest-api/ that “This plugin restores the full functionality of the removed Legacy REST API code in WooCommerce 9.0 and later versions.”
But here https://developer.woo.com/2023/10/03/the-legacy-rest-api-will-move-to-a-dedicated-extension-in-woocommerce-9-0/ you say that it’s recommended that we install it as soon as possible, even before 9.0. What should we really do? Should we install this plugin even before upgrading to 9.0 or no?

Also, how come I’m using the old API and Woocommerce never asked me to switch to the new one? I just don’t get it. I’d never bothered with this API issue until I got the alert in my dashboard.

Thank you for your reply.