It is not an absolute requirement. In case your tickets cannot be scanned during ticket inspection, you will be registered, and you have to show the tickets later to the ticket officer at a SBB travel center. You will pay CHF 30 for each ticket which was not readable during the ticket inspection.
Kindly note, you have to carefully check your tickets. Trainline sometimes sells cheaper tickets for the Milan-Zurich HB route (and v.v.) which are NOT valid on Eurocity connections in Italy yet on regional trains (Transfrontaliera TILO) only. Please confirm you have valid Eurocity tickets before eventually boarding an Eurocity connection.