Tested with no unnecessary modules except for Module Management+
When the Mount button is set to be displayed on the right, selecting multiple tokens and using the Toggle Combat State button makes them try to mount with the same behavior as the actual Mount button.
Similar behavior happens if the button is set to the left and another module adds its button on the left. (For example, Mass Edit).
Foundry v11.308 PF2e 5.4.4 Rideable 2.9.2
Tested with no unnecessary modules except for Module Management+
When the Mount button is set to be displayed on the right, selecting multiple tokens and using the Toggle Combat State button makes them try to mount with the same behavior as the actual Mount button.
Similar behavior happens if the button is set to the left and another module adds its button on the left. (For example, Mass Edit).