This "switching of the plugin" increased my “page time to interact” from around 2.7 seconds to over 7 seconds. Also, the total blocking time went from 30ms to over 500ms.

The person who purchased this plugin and switched it keeps trying to say you installed a free plugin, and can not be upset that it changed. Yes, there are explicit expectations of plugin developers not to do something like this. I am sure it is in the user agreement as well.

Google is rolling out the page experience update and this slower page speed could cost people lots of traffic resulting in millions combined with a 400K multiple to be billions in lost sales. I imagine there could be legal consequences to send a message never to do this again.

This was not someone trying to offer a premium version of the plugin. That is great and reasonable. This was purchasing a different plugin and forcing a radial change that offered no benefit to the original WP User Avatar Plugin users. This one done to get more people on the upgrade path of a different plugin. The result was only broken sites and or sites that were much slower.