You're not wrong - Samsung previously used their own Watch OS called Tizen however since the Watch4 series it has been based on Google's Wear OS with a Samsung One UI skin on top same as the phones...they are Android with a Samsung One UI skin)
Pros and cons with the change but doubt it will change now.
Some of the issues with Wear OS was that it was badly supported and behind compared to competition, but over the last few years with significantly more users and products the development and support has improved and will continue to improve. In fact a new Wear OS 5.0 is due very soon.
It can be more cost effective and efficient for companies to use Google's software and then apply their 'skins' rather than to build a brand new app In house from the ground up and maintain it - this practice is also used In automotive, wider manufacturing and software development.
**Photos IG: @slappa_da_tubs | Videos YT: @gusbandicoot **
