Boarroaquaix75 Hi,
I don’t see any problem. The ticket is valid from Milano to Rivera-Bironico. « Via Monza » or « Via Monza - Chiasso - Lugano » indicate only the route of the train, in this case it is the direct way.
This ticket is not a point-to-point ticket in Switzerland, it covers zones (100, 110, 120, 140, 150), but it is not important for you.
Please note that this ticket is valid only for 4 hours, from 08:43. You can also take the 09:43 service, you will arrive in Rivera at 11:23.
You can see a map of the zones here:
https://arcobaleno.ch/dam/jcr:d8948866-bbe0-4167-b80a-bbf24607f536/2023_arcobaleno_cartina_combo.pdf