Samsung has been using Tizen OS for last few years on its Samsung Gear devices. Evan Blass, a famous leakster posted in twitter that Gear smartwatches running Wear OS were spotted on the wrists of Samsung employees.
Tizen OS gives less number of apps availability over Google Wear OS, other than that Tizen OS gives some additional benefits over Wear OS. Some users might not interested in some additional apps as well. We are not sure whether the Samsung will replace the Tizen OS with Wear OS on all smartwatches or limited to some particular categories alone.