By default tickets are for a route, not a train. Even though you select a train from a schedule to start the booking process, normally that results in a ticket good for a single trip on a route, valid for a whole day. So you can take any train on the route at your own discretion. So missing a transfer, or even laying in a break is not an issue.
Supersaver tickets are the exceptions. These are for a particular sequence of trains, and if you miss a train due to your own fault you indeed cannot just take the next train. If you miss a transfer due to a fault of the railways however (a delay usually) then you can take the next available train.
The SBB will not sell you a ticket with too tight transfers.